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Is It As Bad As I Fear?


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#1 robert.hedges

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Posted 15 September 2020 - 06:35 PM

I've been running in my 1150cc with no real issues. Probably covered less than 150 miles total.

Recently noticed a little smoke upon start up.

Lately getting whiff of petrol from the exhaust.

Went to take it for a spin yesterday and it would not start.

Plumes of smoke later we eventually have lift off, stinks of petrol and hesitates when you accelerate. Though will rev freely.

Pulled each HT lead to see if it was a misfire and no change to engine when cylinder 4 is removed. Changed leads and checked all plugs.

Cylinders 1&2 very sooty, cylinder 3 a little wet and black. Cylinder 4 very wet and black. I could not tell if it was oil, fuel or water.

Clearly cylinder 4 plug was fouling.

Adjusted the mixture and tried to do a compression test and something's clearly not right with my compression tester as they all show 40-45 PSI.... I'll leave that there until I can get another tester to check it. Let's just assume they are ok and the tester is a but dud.

Re-start after the basic clean up and no real change to symptoms. Plugs were still showing same signs after 10 mins Idle and the exhaust smoking and still stinking of petrol.

I'm thinking it's probably the cylinder head gasket, prehaps water in 3&4 causing no spark and unburnt fuel.

Just ordered a new gasket set.

Any other thoughts?

Thanks.

#2 cal844

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Posted 15 September 2020 - 06:44 PM

When you removed the damp plugs, what did it smell like?

I think you may it too rich, what needle is fitted and is it correct for the spec of engine?

#3 robert.hedges

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Posted 15 September 2020 - 06:47 PM

Mostly fuel I think. It's difficult to say with certainty. Looking down the bores the pistons crowns I 3&4 are wet and a little yellow.... is that a sign of oil burning?

#4 robert.hedges

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Posted 15 September 2020 - 06:47 PM

It was very rich I think. Been trying to get to a rolling road.

Edited by robert.hedges, 15 September 2020 - 06:48 PM.


#5 cal844

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Posted 15 September 2020 - 06:57 PM

Yellow sounds like burnt antifreeze, are the crowns covered in carbon or shiny clean?

#6 robert.hedges

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Posted 15 September 2020 - 06:59 PM

Clean I'd say... a little yellow.

#7 robert.hedges

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Posted 15 September 2020 - 07:10 PM

Just lifted the rocker cover.... puff of smoke and petrol smell. I've also noted the inlets of 3&4 are black on the top....

Now I'm thinking it's the stem seals. Both failing though... fresh build? Seems wierd.

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#8 JVA10L

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Posted 15 September 2020 - 07:25 PM

Before going to a lot of trouble I would try having a look at the needle jet and float in the carburettor that feeds cylinder 3 and 4. 



#9 gazza82

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Posted 15 September 2020 - 07:27 PM

Could it be over fueling? SOmething getting stuck and flooding the engine with too much fuel? New ethanol based fuel is great at gumming up or eating rubber seals ...

#10 Moke Spider

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Posted 15 September 2020 - 08:14 PM

Before going to a lot of trouble I would try having a look at the needle jet and float in the carburettor that feeds cylinder 3 and 4. 

 

Almost certainly this will be the issue, the float valve isn't shutting off and raw fuel is just pouring in to it.



#11 robert.hedges

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Posted 15 September 2020 - 08:24 PM

Cheers for your thoughts guys.

Feel a lot more confident in the collective diagnosis.

I'll start at the easy stuff like checking the carb first. All too easy to start researching thinking the worst

#12 sonscar

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Posted 16 September 2020 - 06:32 AM

Choke not stuck on?Steve..

#13 richmondclassicsnorthwales

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Posted 16 September 2020 - 10:26 AM

Check the jets are not sticking on the jet bearings, it can happen.

 

Otherwise as Moke says, the float valves can be stuck open, and flooding the carbs, hence a big smell of petrol and plumes of smoke






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