LCGB Forums

my gp200 std had another heat seize....doing 60/65....back wheel locked up, pulled clutch in, come to a halt, was on busy A12 essex at time,
scared life out of me. Was lucky a guy pulled up in a van, who had a ramp, took me up to service station....let cool down, checked plug, made my way home.
So seems a strip down....but thinking of getting a muggello kit, but would i have to change clutch/crank as well.
got std clutch fitted, and std merc crank.... Any advice?

When you checked the plug, was it white?

it would seem like either your mixture is too weak at 3/4 -full rpm or your timing is a little too far advanced causing the engine to overheat.
Although Its possible your piston is too tight or your rings have insufficient gaps in which case you may need to strip the engine.

There are a few things you could try before stripping the engine or replacing it.

You should do a full throttle run /spark plug check to see exactly what your fuel mixture is at full throttle

Increase the richness of the mixture at 3/4 full throttle by changing atomiser and needle
You back off the advance 1-2 degrees and see if that makes a difference
What oil/petrol mix are you using ? If you are using 4% mineral or 3.5% semi why not try fully synthetic oil at 3%
The more oil you have in your fuel, the weaker the fuel mixture will be and the hotter your engine will run.

hi....firstly i think ive been adding too much oil, my plug has been gold/brown, with black around the ring.
ive done 800 plus miles, mostly short runs, except when I seized up, travelled approx 30miles.this is the plug after i had stopped.

Plug looks good so your carb'/settings look ok. Looks like an out and out heat seize, basically running too hot for too long. possible causes are piston/rings too tight in the bore, cylinder head compression too high.......+ various other

Not sure what a "standard" Muggello kit kicks out but I would have thought a half decent MEC would be ok. likewise a decent 4 plate clutch with strong springs should be ok.

cheers for advise.....

that plug doesn't look good to me at all.

I would say that the mixture was ok at some point because there is a nice biscuit colour to the electrode ceramic ,...but .......something has changed since that time .
There is a heavy coating of carbon and oil which could suggest that you have either got the oil /petrol ratio wrong last fill up or you've lost an oil seal somewhere. That could cause a signifiant change in your fuel air mixture and running.
Might be worth doing a pressure test of your crankcase

OK thanks will do compression check, what is a good pressure....

Yes I think there is a possibility that plug may be a little on the light side but photography can change colours and contrast.
A lot of guys get the wrong idea with regard to rich /weak mixture and wrongly believe that more oil richens the mixture. So wrong !
Petrol is the coolant, the air runs hotter..... that's the important mixture, petrol and air.
2 stroke motorcycle racers would fine tune their mixture by adding a little less oil to richens up and a little more to weaken off.

johnnyXS wrote:that plug doesn't look good to me at all.

I would say that the mixture was ok at some point because there is a nice biscuit colour to the electrode ceramic ,...but .......something has changed since that time .
There is a heavy coating of carbon and oil which could suggest that you have either got the oil /petrol ratio wrong last fill up or you've lost an oil seal somewhere. That could cause a signifiant change in your fuel air mixture and running.
Might be worth doing a pressure test of your crankcase

I disagree,from the photo the colour looks perfect,the earth strap is dark brown and the ceramic insulator is a lighter brown.The carbon build up on the plug is quite normal for a 2t.

HxPaul wrote:

johnnyXS wrote:that plug doesn't look good to me at all.

I would say that the mixture was ok at some point because there is a nice biscuit colour to the electrode ceramic ,...but .......something has changed since that time .
There is a heavy coating of carbon and oil which could suggest that you have either got the oil /petrol ratio wrong last fill up or you've lost an oil seal somewhere. That could cause a signifiant change in your fuel air mixture and running.
Might be worth doing a pressure test of your crankcase

I disagree,from the photo the colour looks perfect,the earth strap is dark brown and the ceramic insulator is a lighter brown.The carbon build up on the plug is quite normal for a 2t.

read what I said

johnnyXSwrote:
"THAT PLUG DOESN'T LOOK GOOD TO ME AT ALL"

I did

garynonnah wrote:OK thanks will do compression check, what is a good pressure....

He didn't mean a 'compression' check, he said PRESSURE check. The pressure or 'leak down test is carried out to check for air leaks in the barrel/crank case area. Kits are available for doing this but a reasonable test can be done using an old bicycle inner tube, pump and some soap bubbles. You would need to remove the carb and exhaust and cut the inner tube and put one end over the exhaust manifold (or stub) and the other over the inlet manifold. Pump the tube up so that there is a fair amount of air in it and then squirt you bubbles around the gasket faces and oil seals to check for leaks.

HxPaul wrote:johnnyXSwrote:
"THAT PLUG DOESN'T LOOK GOOD TO ME AT ALL"

I did

I do not write in capital letters Paul

Might I respectfully request that you read and quote the whole of my post in its entirety
Please do not remove just one small part of my post in order to quote it out of context to imply something that I did not intend.

I respect your assessment and suggestion (although I do not concur ) and your right to voice it
I suggest you offer other members the same consideration

johnnyXS wrote:

HxPaul wrote:johnnyXSwrote:
"THAT PLUG DOESN'T LOOK GOOD TO ME AT ALL"

I did

I do not write in capital letters Paul

Might I respectfully request that you read and quote the whole of my post in its entirety
Please do not remove just one small part of my post in order to quote it out of context to imply something that I did not intend.

I respect your assessment and suggestion (although I do not concur ) and your right to voice it
I suggest you offer other members the same consideration

There's always going to be differences of opinions on here, that's what forums are for. Just give each other a bit of slack guys.

Rich'

Hi guys, just done a compression check, im getting a reading of 75PSI
Im using a NGK BR8ES plug..... and noted plug very oily now, going too take her out for lil warm up
to see what plug is like.....

ALSO drained oil whilst running and revs never altered....so believe drive seal is ok?????

garynonnah wrote:Hi guys, just done a compression check, im getting a reading of 75PSI ...

Read my post above, a compression check is NOT what's needed, you need to do a PRESSURE (leak down) check to see if you have any air leaks.

will do a pressure check next.....