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petrol problems
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Author:  Bubbacluby [ Fri Jun 01, 2007 3:27 pm ]
Post subject:  petrol problems

i have got problems with my 998 mini.. i cant figure out what it is, i thought you fellas might be able to put some light on my situation

If your driving along, say in 3rd about 2500rpm then plant the foot it coughs and splutters, sometimes you think the motor has stalled altogether and then starts up firing again. Its happens bad round corners like coasting round corners then planting the foot coming out.
It goes along at 100-110 ok.

We think it has something to with petrol so weve fiddled with float level and put oil down carb hole and still playing up. Has anybodody got any ideas.

Engine is a standard 998, 1 1/2 inch su, has extractors and new exhaust, and head has recently been rebuilt (slightly shaved but still standard).

Ive no idea.

Brenton

Author:  sports850 [ Fri Jun 01, 2007 4:04 pm ]
Post subject: 

Take the air cleaner off and with the motor idling lift the carbs piston up slightly , if it's running right it should drop in revs slightly then pick up again . If it's running lean it'll run really rough or stall . If it behaves their (the mixtures not too bad ) then it's time to look further , have you done anything to the carb lately , could the manifold be leaking air into the motor ? Have you got a fuel filter anywhere in the line that's blocked , look for the metal fuel line being crushed anywhere , check the rubber fuel hoses to see they haven't started to perish and filling the line with crap . Anyone else ???

Author:  pristic [ Fri Jun 01, 2007 4:19 pm ]
Post subject: 

Could be too much fuel or too little...
Mine does that when you are not on cam yet and not quite warmed up... I think its flooding in my case cause my float level is a bit high.

You should really get it on a rolling road and see what its doing...

Pete.

Author:  Bubbacluby [ Fri Jun 01, 2007 4:56 pm ]
Post subject: 

what do you mean could the manifold be leaking air into the motor ??

Do you mean like a leaking inlet manifold, where attaches to head or hold init or something?

Author:  sports850 [ Fri Jun 01, 2007 5:08 pm ]
Post subject: 

Basically I mean if the inlet manifold doesn't seal perfectly onto the head or perfectly onto the carb . Or if there's any vacuum outlets for a brake booster or anything leaking and letting air into the manifold after the carb . If air gets sucked in anywhere else than through the carb it will make the mixture lean .

Author:  Bubbacluby [ Fri Jun 01, 2007 6:36 pm ]
Post subject: 

ahh ok, yeah i'll have to have a check... thanks for the help.

Ill check it and the other things you mentioned

Brenton

Author:  tom11111 [ Fri Jun 01, 2007 10:31 pm ]
Post subject: 

If it idles o.k. then it will not be an air leak at the manifold, there is not much vaccuum when the throttle is open to cause an air leak. it may be a lean mixture. The float bowl is on one side of the carb, say its on the right and it only runs bad when steering left, the g-force pulls the fuel away from the jet, so tune it richer.

Author:  tinymorris1969 [ Fri Jun 01, 2007 10:42 pm ]
Post subject: 

ive got the same problem at the moment in tiny since i put the carby on, the needle and seat are worn in the float so the car will flood itself at idle but not bad enough to idle bad but bad enough to not allow enough air in, i would look at doing a reco on the carby, ive spent 2 months messing with different oils and needles and ive finally come down to the float, but firstly what carby is it? has any mods been done to the car that will upset the system? i trick glen at mini king showed me is

take ur air filter off and block the air intake with ur hand not completely juz enough to restrict air flow and start reving the engine at around 2500 rpm for about 2 mins and take ur hand off and let the engine back to idle, go for a drive and ull find the problem goes away for a lil while, burns off the excess fuel maybe?

Author:  Bubbacluby [ Sat Jun 02, 2007 10:10 am ]
Post subject: 

Engine is as follows

Engine is a standard 998, 1 1/2 inch su, has extractors and new exhaust, and head has recently been rebuilt (slightly shaved but still standard).
Has original black plastic airfilter.

Idle is a little rough, apparently cam timing is slightly out - but idle had always been a little rough, it hadnt always done this though (cough and splutters

Thanks for your help everyone

Ill look into it and see if they help/fix

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