top end
- clanger9
- Posts: 1163
- Joined: Sat Jun 20, 2015 9:38 am
- Location: Chester, UK
Re: top end
Did you move or loosen the fuel pipe union on the top of the float chamber? If fuel comes out of the inlet, then either the float valve is sticking, the float level is too high or the little spacer on the float pivot shaft is missing (unlikely if Martyn just rebuilt it!)
1989 Moto Morini Dart 350
1993 Ducati 750SS
1993 Ducati 750SS
-
- Posts: 75
- Joined: Fri Mar 08, 2013 12:03 pm
- Location: DERBYSHIRE UK
Re: top end
all, nothing has been done to the engine,last October I had two 20 min runs around the village and thought then as I could not get a good tickover when hot would send to martin bratby, who I think has done a fine job on the carb, fuel is coming out of the carb inlet at some pressure, that's
why I thought something was amiss with the inlet valve.
what is a good cylinder psi for a compression test.
rob.
why I thought something was amiss with the inlet valve.
what is a good cylinder psi for a compression test.
rob.
- Ozmadman
- Posts: 2651
- Joined: Wed Dec 14, 2011 1:02 am
- Location: ESSEX UK
Re: top end
Martin Bratby usually re-seats the float valve seat and fits a brass needle valve as he doesn't like the Viton tipped ones as he says they still stick and that Has been my experience too so I can't see it being that or any other carb problem to be honest as he is meticulous in his work.Duncan wrote:Normally a sticking float/dirt on the seat of the carb fuel cut off.red_dog49 wrote:HI, yes ok but would that cause fuel to exit the carb ????.
Rob.
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
- clanger9
- Posts: 1163
- Joined: Sat Jun 20, 2015 9:38 am
- Location: Chester, UK
Re: top end
Ah, if it's *blowing* fuel out of the inlet, then it's not the carb or float - sorry, I'd misunderstood your description.
Back-pressure through the inlet suggests a valve timing problem, inlet valve sticking open or exhaust valve sticking shut.
I'd check the inlet valve tappet clearance. It sounds like it's too tight.
Back-pressure through the inlet suggests a valve timing problem, inlet valve sticking open or exhaust valve sticking shut.
I'd check the inlet valve tappet clearance. It sounds like it's too tight.
1989 Moto Morini Dart 350
1993 Ducati 750SS
1993 Ducati 750SS
- Ozmadman
- Posts: 2651
- Joined: Wed Dec 14, 2011 1:02 am
- Location: ESSEX UK
Re: top end
just to add if you are unaware, the correct method is no discernible play between rocker and push rod when the engine is just warm (not hot) you should be able to spin the push rod easily. To make sure clanger is on the right track you could always set them with a bit of play just to see if that cures your problem and then re-set them correctly after.clanger9 wrote:I'd check the inlet valve tappet clearance. It sounds like it's too tight.
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
-
- Posts: 75
- Joined: Fri Mar 08, 2013 12:03 pm
- Location: DERBYSHIRE UK
Re: top end
thanks for the replies more checks imminent.
Rob.
Rob.
-
- Posts: 75
- Joined: Fri Mar 08, 2013 12:03 pm
- Location: DERBYSHIRE UK
Re: top end photos
hi, going to find new springs ,pics don't show me any other problem, although i'm happy to be corrected.
You do not have the required permissions to view the files attached to this post.
- clive
- Member
- Posts: 5708
- Joined: Mon Jan 01, 1990 12:00 am
- Location: LONDON UK
Re: top end
I take it that is the inlet valve seat showing. Looks to me as though it is only making clear contact between the valve and seat in the bottom left "corner". If this is the case might the valve be slightly bent? If it is not going fully home then it would tend to blow back out of carb as the engine comes up to compression. I would try lightly grinding it back in and see if you get a nice finish all the way round the valve.
clive
if it ain't broke don't fix
if it ain't broke don't fix
-
- Posts: 75
- Joined: Fri Mar 08, 2013 12:03 pm
- Location: DERBYSHIRE UK
Re: top end
no, that's the exhaust seat.
Rob
Rob
-
- Posts: 2884
- Joined: Mon Mar 24, 2014 5:44 pm
- Location: Aberdeenshire
Re: top end
Hi
You've gone this far so it would be missing a trick to not check both valve stems for evidence of distortion or binding, also to regrind both valves. Once the head is back together you can check the valve sealing by filling the inverted head with petrol and seeing how quickly it leaks away.
Regards Mick
You've gone this far so it would be missing a trick to not check both valve stems for evidence of distortion or binding, also to regrind both valves. Once the head is back together you can check the valve sealing by filling the inverted head with petrol and seeing how quickly it leaks away.
Regards Mick