Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Andy1976 on August 02, 2008, 11:37:52 AM
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I'm still struggling to get my bike started.
I have done/checked - carbs,cleaned out jets
fresh fuel
new plugs with correct gap
batery checked and ok
I'm unsure about checking electrics, all the wires seem ok and conected properly.
Cheers
Andy
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Does it fire/misfire/spit/pop at all? If not then check the 12V side of the ignition.
Are the plugs wet? If so you have fuel so that's one thing off the list as fuel + spark = bang (even if it is a misfire)
If plugs dry then no fuel so check to see what you put back into the carbs upside down... ::)
Off to France tomorrow on my Sprint so won't be posting (much).
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Have you checked for a spark, pull a HT lead off put a spark plug in it, ground it against the cylinder and turn the motor over (kill switch), you should see a spark, as Steve has said wet plugs show that fuel is getting through. You need sparks, that's plugs, coils and electrical trickary, the spark has to be at the right time, points and timing. Is there any power at the points. You need fuel from the carbs, is it coming out of the tank, are the float bowls filling up, you also need air (in the right place), how is the air filter and carb rubbers.
Cheers
Den
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I've been outside this morning working on the bike. It's only sparking on no.3 theres nothing on the others. Since cleaning the jets, no.2 carb is leaking fuel everywhere. The float bowls were full when I took them off.The plugs don't seem wet (no.3 seemed damp), but they do smell of fuel. Maybe a complete carb overhaul? The battery is reading 12.35v so I think this is ok. The ignition system is electronic by Boyer Bransden, should I go back to points system? I also noticed two of the carb rubbers from the airbox have small splits on them, the inlet rubbers seem in good nick.
When I tried to start it before it made a popin noise and also a huge backfire (scared the crap outa next door ;D).
I think I'll be ok sorting out the carbs but electrics arn't my strong point.
cheers
Andy
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Hi Andy, what is the history of the bike, was it running when you got it ?
It would probably be a good idea just to do a basic service on the bike, valve clearances, timing, carb set up etc just to make sure that the basics are correct. Sparks are paired, 1&4, 2&3, if you have a spark on 3 you should have a spark on 2 as well, what condition are the HT leads and plug caps, what plugs have you got.
Cheers
Den
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Hi Den, I got the bike in September last year. It was running lovely and it rode nice too. There was'nt much history with the bike, just a couple of reciepts for a new battery and brake pads and an MOT slip. I have had it re-bored and new pistons fitted(it broke down six months ago).
When you say valve clearances, do you mean the gap between the tappets? The HT leads seem ok but I've noticed a chunk missing from no.2 plug cap. The plugs are NGK DR8ES and D8EA (only jus noticed two different types!)
I have taken off the carbs to give them a good clean. I have found a good reference on the other site which should help with settings.
Thanks mate
Andy
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Yep, valve clearance, tappets, 2 inlet 3 exhaust if I remember correctly, the other site should have loads of info that you can use, sure helped me rebuild my F1.
Cheers
Den
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I'm going to re place the spark plugs as the others were mis matched. Two were D8EA and the other two were DR8ES-L(NGK). The manual says to use D8ES(NGK) or X-24ES (Nippon Denso). What plug would you recommend I use?
Thanks
Andy.
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I've always used NGK's.
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That's a good question, I always used NGK D8ES-L, but they you can't get them anymore, so I got D8ES-L R, these did not work they fouled up very quickly, so I tried D8EA,s, these were better but still fouled. Then I read a thread on the other site in which Hondaman recommended the ND X-24ES-U, I now use these and they appear to be fine.
Cheers
Den
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You dont need resistor plugs "R" if you have resistor spark plug caps.....what plug caps do you have?
Dave
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I'm running resistor plugs and caps with no probs.
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I'm running resistor plugs and caps with no probs.
Why add more resistance in the circuit than is needed, 5k? is what Mr Honda decided was enough why double it?
Dave
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The resistor is there to prevent intereference on tv's and radios etc. and I couldn't get the non resistor plugs so I asked the question on a couple of forums (here as well I think) and the general concensus was it would be OK.
It's running fine on them and I don't cause any interference on anyone's telly or radio.
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Hi Biffta, these are my spark plug caps. I'm not sure if they are resistor or not.(http://i345.photobucket.com/albums/p363/andy-1976/CB750pics/260708mis050.jpg)
There is a number, XD05F 5K?. As you can see one has rubbers missing, will this affect it in any way?
Plug cap NO.2 is damaged so needs replacing.
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If you look carefully on the outside they should be marked 5? if they're resistor caps. IIRC it's embossed into the plastic.
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Hi Dave, it looks like they are resistor caps.
Den, where do you get your ND X-24ES-U plugs from? I've been looking through DS catalogue but he does'nt have them listed, only NGK's. My local spares shop does'nt stock them either.
Cheers
Andy
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Riding with old caps and missing rubber seals is asking for trouble. The first sign of rain and you will be spluttering to a halt.
Not expensive - get new ones!
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Hi Andy,
Had to do a web search for the plugs got them from this firm in the end http://www.camskill.co.uk/, Steve's right about the plug caps, cracked or missing rubbers means lots of fun in the wet, however I did buy 4 new ones from DSS, they are not cheap and within 400 miles one has failed already. So I dug out an old one which seems to work, maybe a good idea to shop around for them.
Cheers
Den
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Hi Steve, I've been in touch with DSS and sorted out some new caps. Replaced all four, just to make sure.
Den,thanks for the link, I'll order them plugs tomorrow.
Cheers
Andy.
P.S. Steve, how did it go in France? Hope you enjoyed it.