bike suddenly stops under acceleration ..

[MattW]

Quite possibly, but I didn't think it would happen on the Thundercat seeing as the carbs were behind the engine AND the radiator.

I guess my caveat re the relevency was appropriate but we were casting about for possible causes.

To paraphrase Sherlock Holmes, if you have eliminated all possibilities but one, then you have found the culprit, however improbable it may seem.

I used to get that happen on my Honda CB250RS single. Always used to freeze with the throttle wide open too, which was interesting until I worked out what was happening

Sorry - totally irrelevant to this thread

In an attempt to mitigate the above waffle, I'll say that my gut feeling is ignition - I'd be checking everything back from the plug caps for cracking / water ingress.

 

[cookie]

rust in the float bowls is another thing that can cause those symptoms.

 

[GEOFFREY DEACON]

Have you ever over heated the bike by running in low idle for some time???, If so , then check the plastic spacer in your Hall effect transmitter for heat distorsion,?that causes static on the rotor and will cut the signal untill it cools down and stiffens again, only to reoccur when hot?.

weird answer could be ignition switch going down under load/lights on etc

 

[brassmonkey001]

Quite possibly, but I didn't think it would happen on the Thundercat seeing as the carbs were behind the engine AND the radiator.

I guess my caveat re the relevency was appropriate but we were casting about for possible causes.

To paraphrase Sherlock Holmes, if you have eliminated all possibilities but one, then you have found the culprit, however improbable it may seem.

Fair enough.
Mine does it in summer on hot days so I'd be very surprised if it was down to carb icing. It does always seem to happen when the fuel level is getting low though, never when the tank is full.

 

[pete.keys]

OK - loads of suggestions - thanks everyone.. now its down to business time..

I took a look on wednesday night but the battery hadn't charged and there was no sparc. My charger seams to charge the odyssey battery really slowly. I didn't think there was any point in proceeding until the battery was up to speed as it would point to things falsely.

Went to work on the bike yesterday and the charger clip had popped off so it still wasn't charged duuh.

So today the plan is to tackle the easiest things suggested here first.

Check for spark which I expect it will (if not skip next three)
Float bowls
Diaphragms
Petrol flow test
Clean electric connectors on the harness behind the headstock
Check for any obvious arc points / cable break down - although I doubt this as its all pretty new
Hall canister checkout/swap
Coil checkout/swap

Luckily I'm working from home for 1/2 day today so should get some hours to look at this. I need to get it sorted as I need to get the bike running for work monday morning

 

[pete.keys]

3 hours in the shed and

float bowls were clean

DAM plasticine carb top screws 3 out of 4 needed drilling out and replacing!!

Jets - pretty clean

Then luckily the spark went all together ...

Cleaned connectors behind the steering head - knew it wasnt really these as they were clean already.

Went for the bean can and as I moved the cable heard an electrical contact ticking. Low and hold a sparc. So looks like the problem is in the bean can connector

then I ... got called in for dinner

hopefully finish it off tomorrow

 

[pete.keys]

R80 g/s needle removal

When I stripped the carbs I noted all the jet and needle sizes.

I couldnt work out how to take the needle out of the slide to see what "level" it was set at. My R80/R100 manual says to remove the nozzle needle screw but mine didn't seam to have this. I stared down the top of the slide but could'nt work out how to take it out.

Its off a g/s so maybe its different?

Any clues?

 

[brassmonkey001]

Nice one! At least you know what it is now. That's the hard part out of the way.

 

[pete.keys]

just an update to say thanks for everyones suggestions - everything is working splendidly fine now. The problem was infact the 3pin plug for the hall canister which had corrosion on the terminals

Spent a few hours pulling the carbs apart and replacing the seals and carb screws

 

[Sylvester]

I'll put money on a duff coil or ignition. I had exactly the same symptoms on a previous airhead. I was convinced it was also fuel but we have basicaly two separate fuel systems supplied by the same tank. If the supply is ok (presuming the fuel is not contaminated) then the bike should not stop totally. Might run rough or pop and fart but to stop totally sounds like a lack of sparks somewhere. I also find that when the carbs get bunged up its the slow speed circuit that suffers first and the bike doesn't start or idles rough or on one cylinder.

 

[Sylvester]

Pah......Just read the rest of your thread. Sorry. Still just goes to show, if you attack the carbs with mole grips its bound to be the ignition circuit!!!!