Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: philward on November 23, 2018, 10:53:07 PM
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I’m still trying to set up the CR750 to run correctly and was making reasonable progress. However, now the bike struggles to start, occasionally fires and runs (10 seconds) really rough before cutting out and won’t start again.
Reminder of initial set up – 836 Cruzinimage standard compression kit, standard carbs/jetting, foam pod filters, Boyer Micro Ignition/power coils, Moonpie race exhaust with K0 baffles (also, race alternator which has light weight rotor and works with starter motor clutch removed). Carbs bench set up (carb piston cut out height)
Here’s what I have done so far:-
On above set up and first start, started 6th kick and run as per video below. Fuel starvation in mid-range when riding.
https://www.youtube.com/watch?v=YmL8YYWeUMo
Put 135 mains in and raised needle to 2nd from bottom clip (2nd richest) – cured fuel starvation issue in mid range (not revved in higher range yet) – occasional back fire through carbs on start up and plugs black when run for a time at low revs (on a run were I was able to keep revs in mid range, they aren’t a bad colour) .
Rev counter sorted by Smiths so timed with strobe – no difference
Checked tappits and Balanced carbs on vac gauges using carb top adjusters (not air screw adjustment as in a Honda workshop manual I have?) – little change (obviously engine well warmed up at this time) – no change to above. At this point bike was running acceptably well except for the occasional back fire through carbs on start up and plugs black.
At this stage was when the bike struggled to start from cold and now only occasionally fires and runs really rough before cutting out and won’t start again.
Noticed that 2 of foam pods had holes in them and thought this might be a result of the back fires through carbs and bits might have ended up in carbs so stripped, blew all jets out and checked float heights. Repaired foam pods with some filter foam I had (will be changing to better smooth flow pods a bit later).
No change
Re-checked static timing – OK. Massive spark at all plugs but all plugs wet (when trying unsuccessfully start).
Can’t see plugs not sparking under compression suddenly?
Your thoughts and advice appreciated
Phil
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Phil, try a new set of plugs, sounds like they might be failing under compression mate.
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That's my natural thought in the circumstances Bryan but thought why would all 4 fail at once! I have DR8ES and NGK Resister caps. Thinking whether double resister (plugs and caps would have any bearing on the running (or failure) when used with Boyer system?
Thinking of going for D8ES
Phil
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Phil, I understand you either have a resister cap or plug but never both? I would try the D8ES plugs as you mentioned and I think your problem will be cured.
Nice video and awesome looking (and sounding) replica.
Dave
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Phil, I understand you either have a resister cap or plug but never both? I would try the D8ES plugs as you mentioned and I think your problem will be cured.
Nice video and awesome looking (and sounding) replica.
Dave
Thanks Dave, just doing a bit of research and found on the .net site that some people have had trouble with the 8 plug in cold weather. Just thinking that this problem only occurred since the cold weather arrived, wondering whether a 7 rated plug Ward be better with this set up I have on the CR?
What do you think?
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It depends on how wet the plugs are, could be a flooding problem from too much fuel ;)
Between 7 & 8 there is not much difference but, always worth a try.
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It depends on how wet the plugs are, could be a flooding problem from too much fuel ;)
Between 7 & 8 there is not much difference but, always worth a try.
It's funny it's happened on all 4 cylinders at once though Graham - that's what's making me think about temperature range of plugs? ((With drop in temperature over period when problem has occurred)
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Def worth trying a D7ES plug. Also, where did you buy your plugs? I had issues recently with a set of D8ES plugs, bought from a reputable source. But, I suspect they were duff units..changed them, transformed the running of the bike...
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The market seems flooded with fake plugs at the moment! There was a thread about it very recently.
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I was also thinking along the lines of Trigger, sounds like an excess of fuel. Does it smell petrolly?
If it's back firing then it's got sparks.
Boyer are very specific about resistance, and you have got commonality of error across all four if you've got plugs and caps out of spec.
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Hairy, I was chatting to the main man at the NGK stand at the bike show. I asked him how do we spot a fake, he said he couldn't tell me as this would get back to the fakers! Very odd, I thought they would do everything they can to publicise how to spot a fake? I mentioned about the logo rubbing off and the core not being made of copper, he appeared surprised. All he could say was to buy from a reputable seller.
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Phil, I understand you either have a resister cap or plug but never both? I would try the D8ES plugs as you mentioned and I think your problem will be cured.
Nice video and awesome looking (and sounding) replica.
Dave
Thanks Dave, just doing a bit of research and found on the .net site that some people have had trouble with the 8 plug in cold weather. Just thinking that this problem only occurred since the cold weather arrived, wondering whether a 7 rated plug Ward be better with this set up I have on the CR?
What do you think?
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Moist, damp, wet air doesn't flow through foam filters very well in the winter. This will drop the air to fuel mix :o You could always leave it to the summer for better running ;)
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Thanks guys (sorry been out all day) - too much fuel theory makes sense except haven't changed anything between good and bad running. Graham's cold damp air comments make sense, I think it's between that, fake plugs and plug temperature range (my set up might be sensitive to this) that makes sense to me. I'll try start up without foam filters, then swap plugs from my standard K2 (although R plugs) them order some none resister 7's from an NGK UK recommended stockist
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Just ordered 4 x D7EA's from Europarts - £8.29 delivered! (discount code END35) - Got to be genuine from a company that size surely!
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Have you done a compression test on it.
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Have you done a compression test on it.
No not yet but this problem has happened suddenly and all 4 plugs wet + thought it's unlikely that valve/bore problem on all 4 pots
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Have you done a compression test on it.
No not yet but this problem has happened suddenly and all 4 plugs wet + thought it's unlikely that valve/bore problem on all 4 pots
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It is. Its just that you have stripped the carbs looking for bits of pods, I suppose its possible for it to have got to and stuck to the valves/seats .Unlikely but a possibility. Stranger things happen at times.
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Hi Phil, which carbs are you running, PD41’s with an accelerator pump?
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Hi Phil, which carbs are you running, PD41’s with an accelerator pump?
Early 750 carbs (screw top type) Mark
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Ok, mine started to get difficult to start, I found that giving the throttle a couple of sharp twists to make the accelerator pump squirt fuel into the intakes and then pressing the starter button regained instant starting, I think maybe my primary circuit is blocked, really must get around to taking carbs off and sorting, obviously you can’t try that because you don’t have an accelerator pump.
First I would try new plugs because it’s easy, but I think you’re issue could be fuelling , so I would..
1. Check the choke mechanism is working correctly
2. Check float heights and check that floats are not Punctured
3. Check the needle valves are seating/operating correctly
4. Check the carbs are receiving fuel from the tank and the tank isn’t forming a vacuum.
5. Give the carbs another clean.
Then, check the inlet rubbers for leaks.
Then alter your float heights away from the standard setting, if it gets better or worse you might be on to something.
Then because my bike ran badly with Pods until I grafted the original intake trumpets onto the front of them which makes me think pods are a bit crap I would get some velocity stacks, this doesn’t fit with your problem suddenly appearing but I think you’ll find the bike generally runs better with stacks, plus they look nice!
Also check your timing with a strobe gun so that you know the advance/retard is working
It will most likely be none of the above of course 🙂
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Ok, mine started to get difficult to start, I found that giving the throttle a couple of sharp twists to make the accelerator pump squirt fuel into the intakes and then pressing the starter button regained instant starting, I think maybe my primary circuit is blocked, really must get around to taking carbs off and sorting, obviously you can’t try that because you don’t have an accelerator pump.
First I would try new plugs because it’s easy, but I think you’re issue could be fuelling , so I would..
1. Check the choke mechanism is working correctly
2. Check float heights and check that floats are not Punctured
3. Check the needle valves are seating/operating correctly
4. Check the carbs are receiving fuel from the tank and the tank isn’t forming a vacuum.
5. Give the carbs another clean.
Then, check the inlet rubbers for leaks.
Then alter your float heights away from the standard setting, if it gets better or worse you might be on to something.
Then because my bike ran badly with Pods until I grafted the original intake trumpets onto the front of them which makes me think pods are a bit crap I would get some velocity stacks, this doesn’t fit with your problem suddenly appearing but I think you’ll find the bike generally runs better with stacks, plus they look nice!
Also check your timing with a strobe gun so that you know the advance/retard is working
It will most likely be none of the above of course 🙂
I've tried 1 - 5 Mark. The foam pods I've fitted have a smooth transition inside without the step on normal pods (read your post!). Probably will be going for stacks longer term and adjust settings accordingly. Have strobed and advancing ok as per Boyer instructions.
I'm leaning towards the way I've balanced the carbs - they are definitely balanced (on vac guages) but with all flooding on all 4 pots (after I balanced them) I'm wondering whether the needles are set 'too high' at start up - if that makes sense. I have an original genuine Honda workshop manual that I'm sure says you balance them using the air screws (? - will re-check manual) - planning to bench balance them measuring slide cut outs distance (as I originally did when it started easily on first start up) then re-balance.
Just waiting for D7 plugs to arrive and try them.
I'm waiting for
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Ok Phil, I’m never sure at times like this if it’s frustrating or interesting, both I suppose, first principle in trouble shooting is “what did I do just before it went wrong? “ so could be something that happened during the balance work if not the balancing itself (which is unlikely to the cause of the poor starting, but I know you know that :) )
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I agree - may be air screw adjustment relative to the balance of the carbs - may get time this weekend to have a look (barring Grand children arriving! I'm not too stressed about it - as long as I get it sorted by the spring!
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How much & how long have you had the fuel in the tank ? this could be your problem
Try draining the tank & fill it right up with a good premium fuel & then add some stabiliser for winter storage, if this sorts out the problem you then need to start it up every month or so until engine is warmed up. hope this helps
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I've only been putting half a gallon in at a time as I have been waiting to get the CR replica fuel tap back from the guy who makes them (as it was leaking) and knew I would need to drain the tank. I have a cr250 motocross tap on at the moment (its not a tap issue as I've had that fitted since start up).
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Just got an hour in the garage away from grandkids. I think it's sorted (hopefully!). Tried messing with gradually weakening the mixture on the air screws - no change. Plugs still all wet.
Put the D7 plugs in and started 2nd kick - tinkered with slight adjustment of air screws and seems to be running fine. Will re-time and road test over the next week whenever the roads are dry.
Tried white spirit on NGK plugs that were in and the NGK lettering not coming off so whether they are fakes, just duff or the D7's are just better suited to the setup and change in weather, who knows!
Thanks for all your input guys
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I always found that once wetted/fouled plugs may spark when laid on the head but fail under compression, only cure was the old Champion plug sandblaster.
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I've only been putting half a gallon in at a time as I have been waiting to get the CR replica fuel tap back from the guy who makes them (as it was leaking) and knew I would need to drain the tank. I have a cr250 motocross tap on at the moment (its not a tap issue as I've had that fitted since start up).
The only problem with putting small amounts of petrol in the bike & leaving it stood for a while is that it will quickly attract moisture which will sit at the bottom of the tank & the watery fuel will be the 1st thing to fill the float bowls..
but I do understand, you will be emptying the tank to fit the new fuel tap so getting half a gallon out is much quicker than emptying a full tank..
PS.. I use Esso Synergy Supreme + 97 [ No ethanol in this, exceptions for certain areas of the UK ]
https://www.esso.co.uk/fuels-faqs
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I use super unleaded in all my bikes to avoid the thernol related problems - until it gets put in that too!
Seemed to have sorted problem (see previous post) - duff plugs.
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I use super unleaded in all my bikes to avoid the thernol related problems - until it gets put in that too!
Seemed to have sorted problem (see previous post) - duff plugs.
Glad to hear you have sorted it !
The only super unleaded that has no ethanol added is Esso Synergy Supreme, all the other brands "Shell" "BP" etc all have ethanol added, usually 10% & this is going to increase... >:(
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I use super unleaded in all my bikes to avoid the thernol related problems - until it gets put in that too!
Seemed to have sorted problem (see previous post) - duff plugs.
Glad to hear you have sorted it !
The only super unleaded that has no ethanol added is Esso Synergy Supreme, all the other brands "Shell" "BP" etc all have ethanol added, usually 10% & this is going to increase... >:(
Unless it has altered very, very recently Our local Sainsbury was unleaded up to 8% and Super Unleaded 3% As I asked.
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Just checked and BP Ultimate has no ethanol in as well - think there's a post on ethanol in fuel on the forum
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The EU was going to enforce the use of ethanol in all fuels (including diesel) from April 2017 but it doesn't appear to have happened. Probably too busy with #@%$. BP Ultimate in the North West is definitely still ethanol free.
This is the link: http://www.sohc.co.uk/index.php/topic,8911.0.html (http://www.sohc.co.uk/index.php/topic,8911.0.html)
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I had this reply from BP :- dated 2014
Thank you for your email concerning the fuel sold by BP.
In "most regions" of the UK our Ultimate Unleaded dos not contain any Ethanol at present (South West UK excluded).
This may of course change in the future as the specification allows up to 5%. If there will be any changes, these will bw shown on the pumps and at the stations.
BP ultimate will never have more than 5% ethanol until January 2017 when it could be increased to 10%
dated 2018, Shell & Ethanol. in the UK, Shell regular unleaded and Shell V-Power unleaded are likely to contain some ethanol, but it will not be present at more than 5% (in accordance with current UK specification requirements
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I had this reply from BP :- dated 2014
Thank you for your email concerning the fuel sold by BP.
In "most regions" of the UK our Ultimate Unleaded dos not contain any Ethanol at present (South West UK excluded).
This may of course change in the future as the specification allows up to 5%. If there will be any changes, these will bw shown on the pumps and at the stations.
BP ultimate will never have more than 5% ethanol until January 2017 when it could be increased to 10%
dated 2018, Shell & Ethanol. in the UK, Shell regular unleaded and Shell V-Power unleaded are likely to contain some ethanol, but it will not be present at more than 5% (in accordance with current UK specification requirements
So this contradicts your original post on ethanol percentages then.
Glad to hear you have sorted it !
The only super unleaded that has no ethanol added is Esso Synergy Supreme, all the other brands "Shell" "BP" etc all have ethanol added, usually 10% & this is going to increase... >:(
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I had this reply from BP :- dated 2014
Thank you for your email concerning the fuel sold by BP.
In "most regions" of the UK our Ultimate Unleaded dos not contain any Ethanol at present (South West UK excluded).
This may of course change in the future as the specification allows up to 5%. If there will be any changes, these will bw shown on the pumps and at the stations.
BP ultimate will never have more than 5% ethanol until January 2017 when it could be increased to 10%
dated 2018, Shell & Ethanol. in the UK, Shell regular unleaded and Shell V-Power unleaded are likely to contain some ethanol, but it will not be present at more than 5% (in accordance with current UK specification requirements
So this contradicts your original post on ethanol percentages then.
No Not Really
I honestly don't think the Petrol Companies themselves are giving us the true content of ethanol in their fuel .
also I do know is its a waist of time asking the petrol station attendants about ethanol content I don't think half of them will know what it is..
why don't you try contacting the petrol companies above by email or letter & see what info & figures you will get
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Believe what you want from the company's front office, 3 weeks ago BP Ultimate in the North West had no ethanol, I tested it myself. It's very easy to do so why not give it a go and see what the results are you may be surprised.
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I had this reply from BP :- dated 2014
Thank you for your email concerning the fuel sold by BP.
In "most regions" of the UK our Ultimate Unleaded dos not contain any Ethanol at present (South West UK excluded).
This may of course change in the future as the specification allows up to 5%. If there will be any changes, these will bw shown on the pumps and at the stations.
BP ultimate will never have more than 5% ethanol until January 2017 when it could be increased to 10%
dated 2018, Shell & Ethanol. in the UK, Shell regular unleaded and Shell V-Power unleaded are likely to contain some ethanol, but it will not be present at more than 5% (in accordance with current UK specification requirements
So this contradicts your original post on ethanol percentages then.
No Not Really
I honestly don't think the Petrol Companies themselves are giving us the true content of ethanol in their fuel .
also I do know is its a waist of time asking the petrol station attendants about ethanol content I don't think half of them will know what it is..
why don't you try contacting the petrol companies above by email or letter & see what info & figures you will get
Ask the retailer it's on their spec sheets what they receive from the distributors . I asked the girls on the tills who didn't know the content but said they would ask and took my number. A day later I got a call from Sainsbury's head office with the information. It's not a secret and I didn't pluck my figures out of thin air.
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The key words are "likely to contain ethanol". Not all BP does it depends where it's delivered from. Only way to know for sure is to test it yourself. It takes a couple of minutes to do, and is so important during the winter layup.
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It is possible to buy a kit that separates the ethanol from the petrol. It was tested by Rupert Paul in Classic Bike a couple of years ago. The downside is obviously you need to buy the fuel in Jerry cans, take it home and separate it using the kit before filling your tank with the good fuel. This will be a real pain but we may not have a choice soon.
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[quote author=CR750 link=topic=17651.msg152447#msg152447
I had this reply from BP :- dated 2014
Thank you for your email concerning the fuel sold by BP.
In "most regions" of the UK our Ultimate Unleaded dos not contain any Ethanol at present (South West UK excluded).
This may of course change in the future as the specification allows up to 5%. If there will be any changes, these will bw shown on the pumps and at the stations.
BP ultimate will never have more than 5% ethanol until January 2017 when it could be increased to 10%
dated 2018, Shell & Ethanol. in the UK, Shell regular unleaded and Shell V-Power unleaded are likely to contain some ethanol, but it will not be present at more than 5% (in accordance with current UK specification requirements
So this contradicts your original post on ethanol percentages then.
No Not Really
I honestly don't think the Petrol Companies themselves are giving us the true content of ethanol in their fuel .
also I do know is its a waist of time asking the petrol station attendants about ethanol content I don't think half of them will know what it is..
why don't you try contacting the petrol companies above by email or letter & see what info & figures you will get
[/quote]
Ask the retailer it's on their spec sheets what they receive from the distributors . I asked the girls on the tills who didn't know the content but said they would ask and took my number. A day later I got a call from Sainsbury's head office with the information. It's not a secret and I didn't pluck my figures out of thin air..... neither did i
Quote:-
I also enquired about it at our local Sainsburys petrol station last year & I was told it had at least 5% ethanol in the super unleaded. I personaly would not buy any supermarket fuel for my bikes.
https://www.esso.co.uk/fuels-faqs
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Had some time over Christmas hols to try and cure a intermittent popping/misfire on the overrun and tick over – to no avail!
Bike runs fine when accelerating and on a steady throttle but pops at tick over and when de-accelerating at lower revs. Its only on number 3 cylinder.
At the start of this post, I had problem of starting (suddenly) and the misfire – as per previous posts (and your help) cured the starting with the D7 plugs but mis-fire remains.
Plugs all between sand and brown (not black) – although not really had decent run
This is my thoughts
Can’t be ignition and coils as fire on 1 - 4 and 2 – 3 at once. Done compression test and 135 on all 4 cylinders (off kickstart as no starter motor fitted). Plugs new and moved caps on 2 and 3 with no change.
Just used a colortune and at tickover number 1 & 4 bunsun blue and 2 & 3 nearer white - adjusting airscrew on 2 & 3 makes no difference to colour of spark (although engine tone obviously changes slightly) – its more difficult to see flame colour on number 2 & 3 due to having to look via a small inspection mirror (colortune mirrored tube hard to fit due to Boyer coil setup in the way) – hence I might not be able to accurately assess colour.
Just taken carbs off tonight to re-check number 3 carb. Thought I’d carefully check the fuel level in float bowls and removed bowls with fuel still in. Noticed that 1,2 and 4 has same level of fuel but number 3 had lower fuel level by 3 – 4 mm! I’m guessing that this may be the issue - weak mixture causing the popping (although no issues on accelerating?)
So, to increase the fuel level, I think I should decrease the float to body measurement by 3 – 4 mm?
Your opinions much appreciated!
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In my experience popping and banging on the overrun, but otherwise running ok, sounds like an air leak into the exhaust, perhaps at the head / pipe joint.
Worth checking first before you play around with float levels.
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In my experience popping and banging on the overrun, but otherwise running ok, sounds like an air leak into the exhaust, perhaps at the head / pipe joint.
Worth checking first before you play around with float levels.
Thanks Dave - I'll check this weekend. The header to head joint design is very basic on the the race exhaust so quite probable
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Phil,
Popping on the overrun / idle is a classic lean mixture symptoms and the lower fuel level in the chamber is an excellent place to start - sure that will go a long way to fixing yout problems.
Andy
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Agree that you've ideally to change the float level to match the others first to eliminate that difference.
As you state, move the float toward the main carb body to raise the fuel level. The fuel reaches the same level "on the float" so wherever you place the float when the fuel valve is closed, then the level will follow. Assume it's the same float, no leaks, and same length needle shutoff valve.
As Dave says though, an air leak at exhaust port area will often give popping on overrun.
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Update on running issue as per previous posts - thought it might generically help forum members, Floats all re-set and sealed the exhaust/head joints on the exhausts. Popping moved to different cylinder! Thought I'd re-balance carbs as I had had carbs off.
Discovered the fault by mistake as I was setting up bike for carb balancing. Took the tank off and instead off filling remote petrol tank (I use when running bike with tank off) from petrol can, thought I would hang the remote tank of the main tank tap so that I could drain some petrol into remote while I was setting up the vac guages. Turned the tap to reserve and got on with vac guages. When I went back to the tanks, hardly any petrol in remote tank as the tap was 'dribbling' petrol out. Turned the tap to normal on and the the petrol flowed freely. As I have been running the bike on reserve due to keeping a minimum amount of petrol in the tank (as if you remember, I was waiting for leaking replica CR750 tap to be repaired by guy who makes them and wanted minimum petrol to drain when re-fitting), this was probably the problem - and the movement of the popping randomly to different cylinders as different float chambers are deprived of fuel.
The tap I have on is the one off a cr250 motocross bike that the tank manufacturer recommends and fits (due to hole centre dimension) - its an aftermarket tap.
So if you are fitting replica taps to any of your bikes/projects, check the fuel flow to avoid any set up issues!
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Simplest of things. Hope that bottoms it for you. Remember on a race motor I ran, we welded a second tap into tank, each feeding 2 carbs, as it was a thirsty beast!! ;D
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More snagging advice needed please! Only a minor issue but irritating. I have a discreet rear light that tucks under the seat hump that includes LED indicators - front indicators are flush fitting (on fairing) with ordinary bulbs. Lithium battery with Electrex narrow race alternator.
Problem is the indicators flash normally without engine running (battery voltage 12.6v) but when engine running the indicators flash fast (battery voltage 13.6v)
From memory, I originally bought an LED specific flasher relay but to double check, I have just bought another LED friendly relay and it now flashes fast with or without engine running!
Is it the combination of ordinary bulbs and LED bulbs that is causing the problem?
Electrical genius' help required please
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Most of the led specific flasher unit I have seen flash at 90 flashes per minute, which is faster than our old bikes did originally. The law says between 60 and 120 flashes per minute, and 90 is smack in the middle of that. Because they are solid state, they continue at the same rate even if a bulb blows, unlike the old bi metal strip type.
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Most of the led specific flasher unit I have seen flash at 90 flashes per minute, which is faster than our old bikes did originally. The law says between 60 and 120 flashes per minute, and 90 is smack in the middle of that. Because they are solid state, they continue at the same rate even if a bulb blows, unlike the old bi metal strip type.
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But why the difference in the flash rates with and without engine running Hairy?
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Solid state relays rely on clean secure earth's, often an engine running, the vibration will improve the engine to frame earth connection, but many other factors come into play. For example, what voltage are you getting at the power feed and earth that actually enter the flasher unit? Also dirt in the contacts of the indicator switch on the handlebars or the wires from that switch to where it joins the main loom? Maybe removing the old flasher unit and installing the new one has cleaned crud out of a connection and improved continuity, to name just a couple of suspects.
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I'll check those points but everything is new - ie, new switches, loom, relay, lights in fact everything except metal work