Engine stumbling when warming up.

[Jeff J]

I know you said you have ruled out ignition problems, but I had what sounds like the exact same problem & applying de-oxit to the Ign. amp. plug/skt pins cured it.

[bigbadbob76]

After adjusting the choke, it's still the same so I adjusted it some more and still no improvement.
I'm convinced it's choke though as if I turn off, floor the pedal and re-start it sometimes solves the problem, not always though.
Depends on temperature I guess.

Get the problem fixed and you can have an extra 15 mins in bed !

I know you said you have ruled out ignition problems, but I had what sounds like the exact same problem & applying de-oxit to the Ign. amp. plug/skt pins cured it.

hmmmm..... worth a whirl, thanks Jeff.

[itchyfeet]

yeh damp can cause lots of problems and Scotland is known for it

[bigbadbob76]

Aye, it's lashing it down out there tonight.
I'll be needing a cabin cruiser not a camper if this keeps up.

[AIR_CHILLED]

After adjusting the choke, it's still the same so I adjusted it some more and still no improvement.
I'm convinced it's choke though as if I turn off, floor the pedal and re-start it sometimes solves the problem, not always though.
Depends on temperature I guess.

Get the problem fixed and you can have an extra 15 mins in bed !

I know you said you have ruled out ignition problems, but I had what sounds like the exact same problem & applying de-oxit to the Ign. amp. plug/skt pins cured it.

hmmmm..... worth a whirl, thanks Jeff.

I'm in the same situation as you, a process of elimination to get it running it's best.

My stalling, erratic idle and choke setting issues were solved by simple stripping down the carburettor and cleaning it in a ultrasonic bath with demineralised water and a citric acid cleaner.
Ultrasonic cleaners are cheap on Ebay.

I did not adjust any choke or idle settings until I knew I was starting from a good standard.

Good luck

[bigbadbob76]

My carb kit arrived today so I'll be doing a carb strip in the near future.
Good call on the ultrasonic cleaner, we have one at work so I'll dip it in there when I get a chance.

[bigbadbob76]

I finally got around to stripping and cleaning the carb.
1-The choke flap was a bit sticky so that could have been my problem.
2-There was also a little curl of solder round the float needle, where it clips into the float.
it wasn't melted there, just used as a spacer.
I guess that wasn't supposed to be there but someone put it in for some reason.
3-Can anyone tell me what the float height should be?
It doesn't seem to be adjustable and haynes doesn't specify it but why else would the solder be there?
It could be causing lean running if the fuel level in the float bowl was low.
Ho-hum.... the joys of old engines.
4-There is also a little bit of white plastic that looks as if a spigot has snapped off above and to the right of the idle bypass solenoid.
Has anyone else got anything there?

[jamesakers]

3. 27.5mm +/- 1mm
4. I've got the same on my carbs, its a bung for the channel.

[bigbadbob76]

3. 27.5mm +/- 1mm
4. I've got the same on my carbs, its a bung for the channel.

Thanks James.
I guess it should be "bunged" then.
I'll make sure it's blocked off.

[bigbadbob76]

This effin auto choke is driving me crazy.
Carb stripped and cleaned, float height checked and it's on the high side at 28.5mm but just in spec.
I found the restrictor in the vacuum pipe for the pull down was blocked so cleaned that out.
All back together and it's still the same.
i'm trying to get my head round how the choke works....
It's fine on the first stage of the cam, choke shut.
It stumbles if you try and rev it on the second or maybe third stage. choke partly open.
It's fine on the fourth stage, choke fully open.
Adjusting the choke thermo unit helps a bit but it seems to keep the choke on the first stage longer so it's masking the problem.
Unblocking the restrictor hasn't made a differance, hmmmmmm.....

She's also very clattery this morning but I'm hoping that's down to a hydraulic tappet draining down.

[Smiffo]

Perhaps it is just opening the choke too early?

I'm no expert, but maybe it isn't masking the problem when adjusting the thermo settings, maybe you are adjusting it to where it should be?

[bigbadbob76]

Could be but I've allready adjusted it a long way from where it was, will try some more if it'll take it.
I guess the spring will weaken over time what with being heated and cooled repeatedly.

[kevtherev]

Plug colour is no indication of mixture...unless it's after a high-speed run.

[bigbadbob76]

Plug colour is no indication of mixture...unless it's after a high-speed run.

Very true Kev.
I'm happy with it's mixture once the choke is off.
Having adjusted the bi-metalic spring some more, it still stumbles in the middle of the choke range but doesn't stay in that range for long so it's usable.
Maybe i just have to accept it will never be perfect. she is 30yrs old after all.
Would be quite a job to convert to manual choke.