I just finished my topend, but have a question or 2 ?
When I checked the new rings for end gap the bottom ring was at the limit ?
Top ring was right in the middle of spec. Cylinders looked good, still see hatch marks. So is this normal or should I have had the cylinders checked-out even though they looked good ?
Bike seems slow off idle, great up top 6k up, bike is piped, Tyga airbox lid, Hi flow reedblock, HRC kit, carbon reeds. What should I be looking at ? _________________
Jetting? Mixture screw? _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
Won't go until RPM come-up. Seems to want to die when under load at start. If I rev it and slip the clutch it's fine. It was not like this before rebuild would drive fine, just not quick when cracking the thottle from idle. Could the power valve adjustment be off cause this? _________________
Hmmm, it'd have to be way off really - and wide open. Have you checked to see if they're working? At idle they should jiggle back and forth. _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
Jiggle from the servo. There shouldn't be any play in the cables, but they shouldn't be so tight they strain the servo either. _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
Well I rejetted down today and no change. The power valves do not jiggle at idle, what does that tell you ? It does move when twisting the throttle.
Make a long story short & maybe a clue.
While I was reassembling the topend my wife decided to have a junk sale and clean-out the garage. Well she ask me for some help carrying a large box and I lightly kicked my tank as I was passing it carrying the box which was very big. Got to the end of the driveway and went back into the garage and noticed a river running towards me. Ha, kick the petcock just enough to drain the tank all over the floor.
Well once I got that cleaned-up, the topend completed. I needed some gas to fill my tank. I had some but don't remember how long I had it, but now I'm thinking that is my problem. I'm going to try new stuff tomorow. _________________
With the ignition off, rotate the valves by hand to their endstop. Then switch the ignition on. Do they rotate back again? _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
I went thru the set-up on this site & everything worked fine. It did what they said it would do when unplugung ang replugging the GPS. _________________
Reckon the problem is psycological then mate - it's all in your head!
Have you had it on a dyno? They're very good for discovering what the engine is doing, and a straight power run won't cost much - £25 or so. _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
It definitly is not in my head, backfire and bog isn't psycological. It didn't do it before the new topend. Thanks for your help though, but I have got to fix it myself ! _________________
Did you do both cylinders? What did you actually do during the rebuild? _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
Piston, rings, bearing, wrist pin and gaskets. Nothing more, basic topend rebuild. Powervalves moved fine so I didn't pull them. Bike ran good prior to that, but it did need rings. _________________
Thanks for all your help Dave. Needles were set all the way down, so it was fine once the rev's were up. Don't understand why it was fine prior to rebuild ? I feel a little stupid, but happy. Thanks Dave. _________________
Hmmm, don't suppose there's a chance you fitted the rings in upside down?
I'm not sure what problems this would create, but I'd suspect a poor seal would be one of them.
The other thing, is that the bike was probably setup for an engine with low compression, and with new rings that'll have gone up and altered your jetting requirements. I would also suspect the compression has changed slightly if there was any carbon build up on the old pistons.
Food for thought... _________________ MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
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