Will idle but wont rev up properly then cuts out

[Larrysworld]

Hi,

Iv had my bike running fairly nicely recently but then I didnt use it for about 2 weeks, and when I came to use it again the other day its developed a problem.

The bike will start fine on the choke and takes a little while to warm up before taking the choke fully off (has always done this). The problem is that it struggles to rev up, the revs will drop and bike will cut out.

Restart the bike, idles fine, rev it up, revs drop and cuts out. It doesnt seem to matter how many revs it builds up it just does the same thing.

The bike has been kept outside underneath a cover so was thinking this may be weather related? Could it possibly be a wiring issue?

Any help would be most appreciated!

[richr]

check for air leaks or could be muck settled in one or more of the jets possibly

ie dirty carbs

[Larrysworld]

Ok thanks. Iv not got a lot of experience with fiddling with carbs but presumably checking for air leaks would require a pressure test (and pressure testing kit?).
Also, does dismantling the carbs to clean them require any specific tools and would you need to re-adjust them afterwards and replace any gaskets?

[richr]

you can test for leaks by just running the bike with the tank off and spraying wd 40 around the rubbers if the revs change you have a leak

no special tools for stripping carbs you may even get away with the old seals

good luck

[RedexRobB]

I suspect its just moisture. If you can get it out for a long run do so, and i would pop a little redex in the tank too to clean the fuel system out. Also worth taking the little end cap off the pipe that runs down the LHS of the engine, its collects water that accumulates in the airbox and will fill with water quite nicely this time of year. You might find a bit white gunk in there too, thats normal, as water and oil from the filter get together.

But i doubt its due to any air leaks or wiring, something like that doesnt happen in a few weeks sat outside.

[Larrysworld]

I suspect its just moisture. If you can get it out for a long run do so, and i would pop a little redex in the tank too to clean the fuel system out. Also worth taking the little end cap off the pipe that runs down the LHS of the engine, its collects water that accumulates in the airbox and will fill with water quite nicely this time of year. You might find a bit white gunk in there too, thats normal, as water and oil from the filter get together.

But i doubt its due to any air leaks or wiring, something like that doesnt happen in a few weeks sat outside.

I suspect your right, Iv not had a lot of time to look at it unfortuantly due to work but have had the tank and airbox off and given the carbs a good run through with redex, helped a bit but still not running well enough to take out for a run cause it wont hold its revs so just ends up stalling after going literally a few feet. When I get time I'll have a look at that pipe and I might take the carbs apart and try giving them a good clean (without adjusting anything hopefully!) I dont really want to take it to a garage if I can help it cause I can imagine stripping carbs isn't exactly cheep

[RedexRobB]

Stripping them is a pretty easy job, long as you dont bend the metal tangs that the float needles attach too your preety much free to take them apart, clean and reassemble without any bother. Just dont adjust the mixture screws (forget where they are but they are external to the carbs).

Might be some moisture trapped in the bowls. Theres allen key screws in the float bowls with some nipples that the fuel drains out of. Could be worth undoing those till it runs dry and see how you go after that. Catch it in a jar or something and if there is anything other than fuel such as water, give the whole system a clean, from tank to carbs.

Always worth getting the plugs out too, see hwo they look. Then cean clean a reset gap if needed.

Something else that has occured to me, the sliding plate that operates the choke, make sure thats free to fully open and close off of the lever. Mine has stuck in the past and might be contributing to why it doesnt rev properly. Just a thought.

[Larrysworld]

Hi guys,

Just a quick update, The carbs did indeed have a load of moisture in them and looking a bit grotty so after a bit of a drain and a clean is running again
So thanks all for your help.

It still isnt quite running properly tho as the revs are talking ages to fall once the throttle has been shut off, seem to hover around the 4000 mark for a few seconds before deciding to drop. Am hoping this will just be a sticky cable or something, Iv only been able to take it out briefly due to time but if anyone knows of the solution to this I would be very greatful so I can get her back out on the road again

[Tirpitz]

Thanks for the update, glad you're getting somewhere. If the hanging doesn't turn out to be a sticky cable then it is likely to be poorly fitting or leaking carb rubbers. Spray some easy start round the rubbers when the engine is running - if the engine suddenly revs there's your problem.