BAD running when up to temp.

bernard lee · Post by **bernard lee** » Sat Jul 14, 2012 11:12 pm

Hello All, I'm back, This g2 of mine is driving me crazy! How critical is the condition of the exhaust valve ? on inspection it seemed in poor condition compaired to the shiney inlet valve, it has clearly got burned to a degree, its flat surface was not flat. There was a lot of build up around it. When i cleaned up the inside all cleaned very well!! with the exeption of the exhaust valve.
Could this be the cause all along ?????????????.

Any thoughts ? Bernard.

1608 · Post by **1608** » Sun Jul 15, 2012 12:49 am

I don't understand, it reads like you cleaned it all up, but put it back together with a burnt, dirty and ill seated ex-valve!!!

Rob Harknett · Post by **Rob Harknett** » Sun Jul 15, 2012 1:00 am

The exhaust valve will be burnt and black compared to the inlet. The valve stem will need a bit of a clean to stop it sticking, but as above the valve & head seating will need grinding in with grinding paste.
Both should show a nice dull matt finish with no pits etc. However this may not be the cause of bad running running when up to temp. Set tappets correctly just in case valves are not closing when hot. Other comments will be made. So try one at a time then you will know the cause in future, Do all & you will not know what caused the problem if it happens again. You may then discover whats happening with your bike. If for eample on resetting the tappets it runs Ok, you'll know next time and perhaps want to discover why your tapptes tend to close.Edited by - Rob Harknett on 15 Jul 2012 12:45:58 AM

Ian5913 · Post by **Ian5913** » Sun Jul 15, 2012 2:59 pm

quote:

Could this be the cause all along ?????????????.

Any thoughts ? Bernard.

With the head off do a leak test and check if its sticking as well. If neither of these are bad then it should not be a problem and it is common for the exhaust to look rough compared to the inlet it works at a hotter temperature. (Sounds daft but the exhaust gasses pass past it at high speed so the valve operates hotter)

If it is sticking or leaking it could be rough running as a result
Ian

paul knapp · Post by **paul knapp** » Sun Jul 15, 2012 4:02 pm

quote: it has clearly got burned to a degree, its flat surface was not flat

I would have thought that says it all re the valve condition!.....it needs re-surfacing along with the seat re-cut to match.
Once they start to burn, they will rapidly deteriorate due to the higher operating temperature they will run at due to less cooling contact they will have with the seat.

saltbox alf · Post by **saltbox alf** » Mon Jul 16, 2012 12:15 pm

What sort of bad running?misfire,spitting back out carb,poping down exhaust? Lack of power?
Have you gone through the basic stuff eg plug condition/gap /temp range,point gap, timing, fuel level in carb/ blocked jet?is condencer breaking down when hot? It's easy to get a fixation on a problem that is not causing the problem! we have all done it.
Unless I have missed a previous post with the symtoms, start at A and work through to Z

Eddison5 · Post by **Eddison5** » Wed Aug 08, 2012 5:11 pm

Bernard, I haven't seen what has gone on before so forgive me if I am going over old ground. As you will know, rough running when hot can be down to the carb. How rich is your mixture? If the cylinder deposits are black then you should look to your carb, it is running rich. The cause may not be obvious, for example, is the air slider fully retracting and are the jets the correct ones?

Ted