9 replies to this topic

[teddy16_4]

Hi

I was wondering if someone could help me out. I have a 998 Mayfair. On starting and cold running the engine is fine, but when it gets warm (not overheated) it starts to judder. It's worst at town speeds. It sounds like the dizzy cap, ht leads and plugs but i've renewed all of them and it still happens. It is blowing a bit from the exhaust manifold (fixing that now) and pops a bit on the overrun.

Any ideas?

Thanks

teddy16_4

[ginigwunkle]

have you checked the plug gap when changing?

were the old plug ends black/white? maybe brown too...

check for air leaks arround the carb and manifold area up top!

[teddy16_4]

I bought some new Bosch plugs with 0.8 mm gaps, these were the right ones according to the Bosch book the shop had. They were browny with a bit of white and some speks.

I'll have a look around the manifold tomorrow in the light.

When I got a new dizzy cap/ht leads etc, i didn't get new points as they looked ok. Do points deteriorate, or just one day burn out? Maybe i should get new ones.

Thanks

[teddy16_4]

I should also mention that when it does this juddering, I have to pull the choke out for it to run ok. There is also a metal hose that is bolted to the top of the clutch housing which turns to a rubber hose..and leads nowhere... not sure if this is related.

One other thing (sorry) it doesn't have a vacuum hose.

Thanks

[alexcrosse]

nah, thats just a breather.

Checked your charging circuit. Run it in the dark (now ) and see if the lights flicker (just a tiny bit) when it judders.

cheers, Alex.

[ginigwunkle]

should it have a vacuum hose?

if yes then thats your problem, should be on a road car tho...otherwise there would be no timing adance.....hence the pop crackle and farting!

[teddy16_4]

The lights are fine, they are good and bright. It's good to know its just a breather, thought I was missing something serious!

The vacuum hose...I can't find anything on it in the Haynes manual, just diagrams of it. Where does it connect to on the carb?

Also, it only seems to get bad once its warm, but if i were to thrash it when cold....it doesn't judder?

Thanks

[ginigwunkle]

there will be a litle black(usually) pipe/tube coming from the carb near where it joins the inlet manifold maybe on the manifold itself,

it plugs in there dont push it all the way on tho leave just a bit from the end,

and it plugs into the dizzy on a similar pipy thing....

[alexcrosse]

the vaccum hose wont be the problem, it only controls the advance and isnt effected by temperature... only vaccuum. If you have to pull the choke out to get it to run good its carburation, check for air leaks everywhere. Check your needle, dashpot, jet (do a mini rebuild).

[teddy16_4]

Thanks for the info, I'll look for a vacuum hose and have a go at rebuilding the carb this weekend. I tightened everything up and saw that the float chamber was loose! This hasn't solved the problem though.

Also, especially after its been warm for a while, it runs on when i switch it off, as if its trying to fight me switiching it off!

I understand this is bad carburation, is this true?

Is the vacuum hose connector on the carb just behind the front bolt for the air filter?

Thanks a lot.