Forum

[jfw]

My 2003 Bullet 500 (Kick starter) with an Amal R930 Carb simply cut out whilst riding a while back. Ever since then I've been head scratching and tea drinking but with very little progress being made to resolve the issue, whatever that maybe.


Now I'm thinking carb because after kicking the bike over a number of times the spark plug comes out as dry as a bone. That suggests that there's no fuel getting into the mix. I've dropped the jets out of the carb but they look clean as a whistle and have blown through them and seem perfect.


I'm now sort of clutching at straws and have taken the carb totally off the bike and plan to give it a good clean over the weekend but I'm not confident that that will make a difference as the jets seem clean. It must be the carb however so short of buying a new R930...


Now with the exhaust off the bike and with my hand over the outlet port there's some suck back there when I kick the bike over but the compression on the bike is good. Still the suck back was making me think maybe there's no suction on the carb side, so no fuel getting pulled into the cylinder. I sort of can't imagine that to be the case as I was cruising along when the bike simple cut out. I wouldn't have thought that a valve problem would have suddenly appeared.


Spark seems good and strong which ain't conclusive but the fact that the spark plug is dry has to be the starting point. I'll give the carb a good clean. Ponder getting a replacement and drink more Tea.


I know I've not asked a specific question here but just wondered if somebody can see a train of thought which I've not taken? Thanks and hope I don't cause too much head scratching on your part.

[Mark M]

Have you checked fuel is actually getting to the carb? There is a filter in the petrol tap and another in the union that joins the petrol pipe to the carb, I'd check those. It's also possible that the airhole in the petrol cap is blocked, another easy to check thing to eliminate!
REgards, Mark

[Anders F. R.]

And I take it you have checked that the float needle isn't stuck, or the fuel inlet blocked? Regards, Anders F. R.

[jfw]

The Carb tickles just fine and stops the fuel flow when I take my finger of the tickler. I'm blessed with a transparent fuel filter between the tank and the carb so I can see that fuel is moving. Well when I tickle I can see it moving when I'm kicking I can't, I'm not that flexible any more


thanks for the replies there have been no detractors from the carb line of inquiry so I hope I'm on the right track.

[Gwilly]

Hello JFW, That valve thing you mentioned, i.e. the slight suction at the exhaust manifold, i'm sure is quite normal.

Basically to do with valve overlap, You did well to feel it.. If you have compression then thats not your problem now...

Carb problem is possible, but usually accompanied with a misfire or two just before cutting out at cruising speed...

Thats when you fumble for the reserve tap as the truck gains ground behind you. ha ha

Remove the plug and place a piece of clean cloth over the hole, kick away and see if the cloth is moist..

Sniff it.. if your not sure, take it outside and try lighting it... maybe water... If so drain tank..

Given that most carb probs are electrical, i would first change the plug and check the coil, HT lead and cap.

Other opinions are available... gwilly

[PeteF]

I agree it's probably carb if you can't wet the plug at all but could be worth checking that the timing hasn't slipped. I had this once, backplate just came loose.

[Alan R]

Hi guys-------------As per GWILLI re}--Valve overlap...That slight suction at slow speeds is quite normal..... at 5,000 rpm it hasn't time to take effect.....Also with him regards swapping the plug first.. Sorry JFW but contrary to urban folk law you actually WON'T be able to give your carb a thorough clean by traditional cleaning methods alone......ULTRASONIC is the way to go, even though this is more for the idling and 1st stage drillings etc............... take a look at this}----------- http://www.youtube.com/watch?v=xhGyK6MpkOQ --------------- Can't you BORROW another running R930 to prove your carb is actually the culprit ??--------- Just to re-visit the scene of the crime, so to speak-- can you be a bit more descriptive in the way in which the bike "simply cut out" ??? That seems to indicate a clean, electrical break to me ....But you say there is a good spark ?? What colour is it and does it give a "crack" sound when working ?? ------------- have a look at the points---do they seem burned, pitted or generally poor in appearance ? Change the condenser (capacitor), they don't cost much )........ This may be an intermittent, electrical fault --- the type you give to Apprentices that is !!)............ Keep the faith, Brother !!

[Bullet Whisperer]

I would be having a look to see if the inlet valve is actually opening, you may have a dislocated pushrod, or something similar and you would still feel compression of sorts, also the 'suck' at the exhaust port would be self explanatory if this is the case. cheers, Paul.

[Leon Novello]

Usually if it is a fuel problem,the engine tends to splutter rather than suddenly stop. My Bullet would suddenly stop, the mechanic found that the chassis ground wire (earth) was loose behind the left-hand tool box. Tighten connections before major surgery.

[Gwilly]

JFW, you say the compression is very good.. Also you say the carb is off for cleaning, BW has a valid point re the inlet valve, can you not use a light and look in the inlet port. see if the valve is moving freely when you turn the back wheel, in gear/plug out... Check the pushrod for movement...