Honda-SOHC
SOHC.co.uk Forums => The Black Bomber Board => Topic started by: mo goldie on December 11, 2024, 06:42:07 PM
-
Hi
Just a quick one if there is such a thing lol
Just went to my bomber and Tried to start it for the first time in a month and it wont start. it seems to soak the plugs up with fuel. had the same before and it done this from cold even mouths ago and it did the same and it was Not cold weather either. don't know if any one else has had any of that sort of thing before too ?
I have tried with No choke to start and also half choke and full choke but still wont start..... take the plugs out and they are wet give them a bit of a blow lamp put them back in and she starts.
cheers Mo
-
More of a talk it through than explicit direction from me :)
Unfamiliar with the exact method of choking, so more detail needed.
CV carbs are a little different in this aspect as cranking it with the airslides effectively closed runs the mixture rich until vacuum starts to pull them up into correct range.
Engine needs enhanced (abnormal vs warm running) mixture to cold start, an obvious statement, but if no combustion occurs, then relatively easy to siak the plugs.
In attempting a from cold start, try some more (in addition to your already attempting variation) method.
1)crank with no choke or throttle opening at all, just keep trying it to see if it even coughs. No response, then remove plugs to see if wet after that.
2) just a small throttle opening 1/16th turn constant and repeat above. Will expose airslide to more vacuum with throttle plate slightly opened. Judge as above with plugs to see if the results are any different in plug wetting.
With both, get ready to bring a small amount of choke in IF they fire to keep it running.
This just to see if you can influence it like that.
-
Are so that sounds Like a job to try then ? as I was just going right for full choke all the time, so I will give that a try when I get the chance to go have a go at starting it again Next time and try to start without choke then if she fires up put a bit of choke on then.
Thanks for that ;D
-
Have you checked for a spark yet?
-
You could just cheat with some cold start spray into the air filter chamber.
-
I would warn against Easy Start. I have heard, albeit anecdotally, that it removes oil from the bore and can increase cylinder wear cylinder. Of course, this may be humbug?
-
Its definitely harsh in Diesels, I had an issue with a 5 cylinder Merc engined Jeep that started to be a pig to start in the winter. The fault turned out to be seal failure in the plastic based injector pipes that were pulling in air.
I doubt an occasional use on a petrol engine would be an issue. It's surprising how little you need to use if you give it time to vaporise.
Back in the 1970s there was a rumour that engines became addicted to Easy Start type products.
.
-
Adicted is a myth, if you need ether there is usually a fault that needs rectification which only gets worse but isnt looked at because it starts with spray
-
Oddly enough Bryan our WJ would only need the Easy start once on a day during extreme cold weather, for the remaider of the day it would start normally. One day when I opened the bonnet, I happened to see air in the injector pipe system that were starting to loose their transparency due to age. It's the same 3 part injector pipe loom used across a variety of 5 cylinder Mercs. Google search revealed the cause was O ring failure on the pipes, they did not leak fuel due to the high pressure but when cold they would let air in between the two stage fuel pressure system.
As I was still working at MB Derby I priced up the two pipe looms, trade to me they would have been around £300 ish. Armed with the Merc rather than the Jeep part number I found a set of Mopar ones from somewhere odd like Slovakia on e-bay, they came in a Mopar Bag, inside the three pipe looms came complete with the seals & caps all marked as genuine MB parts cost me £125.99!
-
Those price differences dont surprise me mate, O.E. seem to add a "label tax"
-
I agree totally Bryan, me & my mate Ged always comment that these days it's often impossible to know the acual cost price of items.
This conversation generally takes place on our Wednesday Pub Lunch meet where we put the world to rights taking a lot of opinionated crap, adjoining tables often join in on our discussions. Who says only the French have a Cafe type Society.
-
I am not predjudiced-----------i hate everybody!!!!
-
Hi Guy`s
Just anther update of today, went out to try and start the Bomber it still would not start :-\ so took the spark plugs out and they were soaked in fuel.... as soon as I done and Alan Milyard trick of the blow lamp on them put them back in she started right up .....so Must mean for some reason that is making the the carbs..... flooding the bores :D
-
Well I have just got the bomber out to give it a look over and still got the problem with the starting from cold. if it run on the day it will start first push on the button for the rest of that day. leave it over night and get the same thing it wont start >:(
take the plugs out and they are wet.....do an Alan Milyard on them with the blow lamp put the plugs back in and she starts and run fine for the rest of the day, its got all the right Jets in Etc .... but still think it runs to rich tho well richer than I would like ::)
just cant work out why it will Not start from cold....also tried No choke half choke full choke still don`t start.
Need a lay down I Think............ as don`t know where to go next ?
-
In the absence of knowing the engine history, my first thoughts are do you have good compressions?
-
My first thought would be float height but i am sure you checked those repeatedley or leaking float valve along with leaking tap overfilling floatbowls very slowly
-
Hi Ted
Yes I have but as said it starts as soon as you take plugs out blow lamp them put back in and its starts right up.......just seems to flood the plugs with fuel :-[
-
I'm trying to think outside the box now, as a general rule in my experience on an otherwise healthy engine.
If the ignitition timing is spot on it will fire as soon as petrol is in the cylinders.
If the ignition is over advanced it will fire and stall almost immediately.
If the ignition is too retarded it will take a lot of cranking to fire from cold.
Could it be that your ignition is retarded?
The long period of cranking is wetting the plugs so it does not fire, warming the plugs cheats the system so it fires as the plugs are warm giving the warm engine scenario.
-
The symptoms you are getting, including the perception of generally being too rich in running, along with this cold start, suggest the carb diaphragms maybe not perfect in their sealing.
That would have the effect of not raising the main airslide in correct proportion to throttle opening. CV are a little inverted in this aspect as having that slide sit too low will increase vacuum under that slide, forcing a rich mixture as result.
You could try ... just to gauge effect ... starting cold with no choke and holding the throttle at least 3/4 open, but get ready to shut it if it fires at all. This would try to expose the air slide to higher vacuum (hopefully to lift it higher initially) from engine draw and prevent the mixture going too rich during cranking. This is just an exploratory test to see if there's different response, not overall strategy.
If there is a benefit, then that too would point toward very careful inspection of the diaphragm and evaluation of those.
-
well I went out again today or should I say yesterday Now ;D
first job I did try opening up to half and No choke Not a fire, so 1/4 choke No fire so the 3/4 and then full choke still No fire, so took out left plug and done the blow lamp on that put it back in and it fired and started up went out for a 30 mile ride back at lunch time.... went back down at and about mid afternoon first press and away she went and again at tea time hit the button and it started first press.......
I took the slides out a few days ago and checked both needles made sure the Diaphragm's were all nice and smooth running up in the bores and in the body's with now hangups ..oh and I even tried replacing the needles too just incase they were at fault just don't get it....
timing is all spot on thats all done By Electronic Ign now and the battery is up around the 12.8 volts and new ish 8 mouths ago. but as I say after it went out and come back all fine...........but will try it again in the Morning as I might go for a ride again and we shell see... unless it go`s back to blow lamp plug or plugs again we will have to see :-\
-
As you note, its quite puzzling when things look all in order. Frustrating too, but at least you can get it out and running once over that initial part.
Further enquiry :) have the carb CV springs been changed or can you identify them as correct ? It's from your comments about thinking its generally rich overall by a small amount, which the spring will ultimately control in a CV carb and obviously in paired operation with jet and needle.
Another thought, have you tested compression to get a baseline psi figure for each cylinder ? That would be helpful to understand.
-
As you have checked the timing, presumably also the mechanical advancer (if your electronic ignition system one).
I'm minded to agree with Nigel (K2-K6) check the compressions.
Many decades ago I rebuilt an engine that just would not start Circa 1978. I checked & re-checked everything, all seemed spot on. My late father suggested a tow start! The engine fired up and it drove great, when I returned home after a short drive I parked it on the driveway. I went back to it several times that day, it started on the button.
Next morning I flattened the battery trying to start it. A compression check revealed poor compression when cold, quite acceptable compression when hot. It was early December, engine stripped down and block re-bored. I collected the block on Christmas Eve, I spent part of Christmas Day rebuilding the engine (newly married aged 30) , it was fine after the second rebuild. I always blamed the loss of compression on over enthusiatic use of a glaze breaking tool, I had fitted new piston rings as well.
If your compressions are good, could poor spark quality be the culprit?
I might have dreamt it, thought I have read somewhere that plugs spark easier on a hot engine.
-
I would try another set of plugs to see if there's an improvement. And check that the plugs have a healthy spark.
-
Or switch the plugs from the working cylinders with the other two.
-
It's a bomber Ted, it's a twin cylinder bike ;) ;)
-
It's a bomber Ted, it's a twin cylinder bike ;) ;)
Oops I was getting confused with Mikes 550, my bad.
I'll get my coat....
-
Some further points in considering what may be causing this problem.
Try starting as normal BUT with a spare plug connected to one of the leads. Leave the fitted one's in situ though, this to check if there's spark from ignition under cranking load with both cylinder in compression. Its more of a battery check and its capability to supply starter AND ignition circuit simultaneously. Some ignition system are susceptible to voltage "floor" which could be being breeched at cold start attempt.
Digital volt meter on battery to watch the peak drop would help for information too.
Could try connecting it to a car with jump lead to attempt start, that to give higher voltage in regards to above analysis. Is kick starting possible ?
Seems like fuelling is reliably there as the plugs get wet. Possibly too much, possibly spark absent under load as discussed above.
If plugs will run in normal conditions, I'd not have great suspicion of them as faulty.
-
Hi All
Well thanks for all the suggestions as I will have to try them out, i did start her up today from cold and it did start...but on one side the right so took the left plug out and done the blow lamp job on it and fired on both, Now I have done the changing over of plugs and tried New plugs as i have 3 sets did Not make any difference so Not plugs that are at fault,even went and changed the coils out at one point still No difference.
getting back to what K20-K6 about the springs I never had springs in there when I got the Bike but as Ashley said about the kit you could get.....or should I say used to get due to the 4,000 flat spot I did get some springs in the end and put them in, but I must say I never had it running without springs so don`t Know if Not having them would be a good thing to try them without them ? so at some point I will have to give that a try. also I will have to get round again to do a compressions test and check that out too.
-
Reading this thread I've learnt that the Honda CB450 is firstly a two cylinder bike, I had a look at the manual in Ash's dropbox to see what the carburettor design was like.
At first glance it reminded me of the old SU design fitted extensively on British Cars, I'm assuming that the carb here has butterflys that when opened cause a vacuum to raise the needle, Mo Goldie has a springs fitted presumably to dampen the carb piston unit response.
This quote based on Wiki information explains how the SU design works, interestingly it mentions motor cycle applications, none of this is likely to be of any help with the cold start issues. I just found it interesting, others here might too. Back in the day I would tinker with twin carb'd Minis, changing spring colours, using thinner damping fluids plus sometimes fitting different needles.
My quickest ever ADO15 Mini was a 1310 S that was extensively tuned with BL 731 camshaft, mirror finish gas flowed cylinder head etc, etc.
The strange thing was I fitted twin 1.5" Stromberg Carbs rather than the SU ones, it was called an Alexander Conversion. A bit off topic I know but some here will also have /had/owned similar tweaked vehicles. I found the Strombergs superior in my particular engine, certainly not saying they are any better.
SU carburettors feature a variable venturi controlled by a piston. This piston has a tapered, conical metering rod (usually referred to as a "needle") that fits inside an orifice ("jet") which admits fuel into the airstream passing through the carburettor.[20] Since the needle is tapered, as it rises and falls it opens and closes the opening in the jet, regulating the passage of fuel, so the movement of the piston controls the amount of fuel delivered, depending on engine demand. The exact dimensions of the taper are tailored during engine development.
The flow of air through the venturi creates a reduced static pressure in the venturi. This pressure drop is communicated to the upper side of the piston via an air passage. The underside of the piston is open to atmospheric pressure. The difference in pressure between the two sides lifts the piston. Opposing this are the weight of the piston and the force of a spring that is compressed by the piston rising. Because the spring is operating over a very small part of its possible range of extension, its force is approximately constant. Under steady state conditions the upwards and downwards forces on the piston are equal and opposite, and the piston does not move.
If the airflow into the engine is increased - by opening the throttle plate (also known as the "butterfly"), or by allowing the engine revs to rise with the throttle plate at a constant setting - the pressure drop in the venturi increases, the pressure above the piston falls, and the piston is pushed upwards, increasing the size of the venturi, until the pressure drop in the venturi returns to its nominal level. Similarly if the airflow into the engine is reduced, the piston will fall. The result is that the pressure drop in the venturi remains the same regardless of the speed of the airflow - hence the name "constant depression" for carburettors operating on this principle - but the piston rises and falls according to the rate of air delivery.
Since the position of the piston controls the position of the needle in the jet and thus the open area of the jet, while the depression in the venturi sucking fuel out of the jet remains constant, the rate of fuel delivery is always a definite function of the rate of air delivery. The precise nature of the function is determined by the profile of the needle. With appropriate selection of the needle, the fuel delivery can be matched much more closely to the demands of the engine than is possible with the more common fixed-venturi carburettor, an inherently inaccurate device whose design must incorporate many complex fudges to obtain usable accuracy of fuelling. The well-controlled conditions under which the jet is operating also make it possible to obtain good and consistent atomisation of the fuel under all operating conditions.
This self-adjusting nature makes the selection of the maximum venturi diameter (colloquially, but inaccurately, referred to as "choke size") much less critical than with a fixed-venturi carburettor.
To prevent erratic and sudden movements of the piston it is damped by light oil (20W Grade) in a dashpot, which requires periodic replenishment. The damping is asymmetrical: it heavily resists upwards movement of the piston. This serves as the equivalent of an "accelerator pump" on traditional carburettors by temporarily increasing the speed of air through the venturi when the throttle is suddenly opened, thus increasing the richness of the mixture.
SU carburettors do not have a conventional choke flap, which in a fixed-jet carburettor enriches the mixture for starting the engine from cold by restricting the air supply upstream of the venturi. Instead a mechanism lowers the jet assembly, which has the same effect as the needle rising in normal operation - increasing the supply of fuel so that the carburettor will deliver an enriched mixture at all engine speeds and throttle positions. The 'choke' mechanism on an SU carburettor usually also incorporates a system for holding the throttle plate slightly open to raise the engine's idling speed and prevent stalling at low speeds due to a rich mixture.
The beauty of the SU lies in its simplicity and lack of multiple jets and ease of adjustment. Adjustment is accomplished by altering the starting position of the jet relative to the needle on a fine screw (26TPI for most pre-HIF versions). At first sight, the principle appears to bear a similarity to that of the slide carburettor, which was previously used on many motorcycles. The slide carburettor has the same piston and main needle as an SU carburettor, however the piston/needle position is directly actuated by a physical connection to the throttle cable rather than indirectly by venturi airflow as with an SU carburettor. This piston actuation difference is the significant distinction between a slide and an SU carburettor. The piston in a slide carburettor is controlled by the operator's demands rather than the demands of the engine. This means that the metering of the fuel can be inaccurate unless the vehicle is travelling at a constant speed at a constant throttle setting - conditions rarely encountered except on motorways. This inaccuracy results in fuel waste, particularly as the carburettor must be set slightly rich to avoid a lean condition (which can cause engine damage). For this reason Japanese motorcycle manufacturers ceased to fit slide carburettors and substituted constant-depression carburettors, which are essentially miniature SUs. It is also possible - indeed, easy - to retrofit an SU carburettor to a bike that was originally manufactured with a slide carburettor, and obtain improved fuel economy and more tractable low-speed behaviour.
One of the downsides of the constant depression carburettor is in high performance applications. Since it relies on restricting air flow in order to produce enrichment during acceleration, the throttle response lacks punch. By contrast, the fixed choke design adds extra fuel under these conditions using its accelerator pump.
-
Absolutely spot on Ted, they are all but the same principle with only the seal (rubber diaphragm vs SU labyrinth) and air damping vs oil type, but operation is the same for all three mentioned.
One observation in "At first glance it reminded me of the old SU design fitted extensively on British Cars, I'm assuming that the carb here has butterflys that when opened cause a vacuum to raise the needle, Mo Goldie has a springs fitted presumably to dampen the carb piston unit response." this sentence though to clarify, the spring doesn't "damp" as such but changes the resistance against a force.
In this case it changes now far the slide ultimately moves proportional to the vacuum imparted onto it via the slide.
The effect of this is to make it richer if heavier spring is used, or leaner if a reduced spring is used. Thats without changing needle or jet size.
I don't know if they were originally run without a spring and one was specified to adapt OR if it was originally fitted with a different spec spring, then changed to the one Ash advised. Ash would be the source of that detail though in confirming what's what.
-
Extrapolation of effects in this case:- if fitted with stronger spring Or originally had no spring (correctly for that carb) then it will be richer running from straight off the bat to full power with this current spring fitted.
Failure to start and assuming spark is there (plugs verified) with that voltage while cranking test showing anything of use. Then rich can give no effective combustion as the mixture fails to ignite simply because the fuel droplets that are nucleus of combustion aren't volatile enough to start process going. Just gets worse the more it's cranked over. That verified by then cleaning the plug with heat gun.
If it's verified that they can run with no spring fitted, that would be a good assessment to gauge effective starting. I'd make sure that the plug was very tight onto it's gapping spec though, this to try and mitigate the "expected" flat spot that the revised spring is supposed to cope with, as that condition is, or should be, lean running.
-
The manual I looked at CB450 KO shows no spring on the carbs tops.
-
yes Ted you are right they did Not, But as Ashley told me that due to the flat spot around the 4,000 RPM that Honda got a kit out to Try to sort that out one of the things along with the jets needles etc was to fit a spring.
-
The question would be then "does it change anything in starting either springs removed ? " to find out IF there's an effect caused or propagated by them.
Then to bring other questions about running if there was positive change with that.
With electronic ignition (thought it was mentioned previously) some difference in fuel composition now to when that adaption was specified, what is the current situation.
-
yes that will be the next thing to try.......... oh and the fuel well what can I say dam E10 stuff all our old engines don't like that at all ha But I run all my bikes on the super UNleaded.....bring back 4 starr ...ok NOT then lol.
hope to do that some time next week when I get all the Hospital appointment done I will see how it all go`s thank till then.
-
[attachimg=1]
The manual I looked at CB450 KO shows no spring on the carbs tops.
-
Anyone notice the last paragraph, out for richer, in for weaker but is contrary to normal Honda practice, meaning it’s normally in for richer and out for weaker. Exactly what we all, well most of us, thought.
-
Hi all just and update again,
I took the tops off the carbs today and noticed that the left kept getting stuck in the top hat so after cleaning and a bit of polish they both now fall up and down freely with the springs on and off, one thing I did Not say is the springs that I have are honda but from anther bike as could Not get the ones that Honda did for the upgrade kit for the Bomber,
So if anyone has got any of the right ones part Number 6186-283-305 if they know what the lengths of them are as the ones that I have are 8cm long, they were 12cm long but I cut them down as they were far to strong to push up on the piston so I cut them down to counter act that. so if you know the true length I think that will help.
-
Hope you're well after hospital trip.
Ah ha, the springs are definitely suspect then.
Cutting them actually increases the spring strength, but reduces preload. Both of which you don't want in this situation.
Definitely try without them then, and would likely give some credence to your running observation of rich mixture (from having the spring too strong) it fundamentally alters the whole mixture landscape.
In effect, a stronger spring changes the vacuum under the airslide (by altering balance equation above and below) to suck too much fuel through the main jet, irrespective of it's size. Usually you'll get very quick response when you wind it on, even under load, but over fuelling that'll do for your oil by diluting it through washing past the piston rings the excess and unburnt fuel.
Interesting to here any significant change in response without the springs.
-
Spring Spec. for 16186-283-305
Spring Rate 1.3 gm/mm
Free length 71 mm
Wire size 0.55mm diameter.
Outside Diameter 17 mm
-
Do you also have the original jet size spec to compare with that modification sheet Toko_jo ?
I'm interested in what they've changed to gauge the effect they where delivering.
-
Do you also have the original jet size spec to compare with that modification sheet Toko_jo ?
I'm interested in what they've changed to gauge the effect they where delivering.
Some of the kits put together by Honda UK's UK Service Centre in Nottingham in the 1960s contained a #130 main jet (STD was #125) Hope that helps!
-
Thank you, yes helpful.
Anything also on the idle jet details given too ?
-
Thank you, yes helpful.
Anything also on the idle jet details given too ?
Slow and pilot jets in the upgrade kit were both #35 size.
-
testing...
-
Interesting to hear if you get any changes. Well, desirable changes at least :)
-
Hi everyone this is just a test as I have not been able to reply as keep getting a forbiden notice I have had a word with steven and done what he said but it still wont let me get on there :(
so just trying a different pc so here go`s lol
-
Several of us had that notice yesterday morning but works fine now!
-
Hi everyone this is just a test as I have not been able to reply as keep getting a forbiden notice I have had a word with steven and done what he said but it still wont let me get on there :(
so just trying a different pc so here go`s lol
Hopefully you'll get sorted Mo and be back in communication.
For info, I'm just on a tablet running android with no pc as such.
-
Hi every one .....I just can not seem to post anything :(
well Not on my main PC anyway.
are it just worked so I dont know what was wrong but it seems to work ok now...well for a bit ha LOL