Bore kit troubles By erikegbert (Read 1,019 times)

[erikegbert]

I had a guy install my 72cc bore kit and he gave it back to me slower than when it left. He says its because of it not having an exhaust or k&n style air filter. Plus he said that the carb needs rejetting. Now my scooter wont run at all. I need help!! I put on the new air filter and i have a pcv valve to put on the hose from the crank case and a #88 jet to put on the carb. Should i have gotten more power and higher top speed from the bore kit without other mods and also why doesnt it want to start now?

[Alleyoop]

Just a bigger bore kit is not going to give you much of anything. Now you need more air and gas to feed the hungrey hog. Without at least that it will probably be slower than before.

When you say it does not run anymor how do you know it is slower than before. So it was running when you got it. What did you do after you got it that now it does not want to start.

[erikegbert]

It is gettin spark and it is getting air. It was running the day the guy dropped it off to me at work. I drove it home and the next day i tried to start it and it wouldnt turn over. It killed the battery. Since than i have took the air box off and put on a k&n style filter as recommended but that didnt help. I can get it to kick start from time to time but it only runs for a minute than stalls out and wont start again. I have a #88 main jet that was recommended to install but havent got it put in yet. I also put an air in pcv valve that i put on to help with the vaccum. Im waiting for a new idle jet to arrive in the mail now.

[Alleyoop]

Erikegbert,
If its a 4 stroke engine I would check the valves, the ride home could of tighten them suckers up if he did not lap the valves and or adjust them. It is probably a combination of things, but start with adjusting the valves since its a new BBK, then you can work on fuel delivery issues
that you may have. With the K&N filter you will need to probably re-jet to match the air intake.
Try this take the filter off and cover the Carb intake with your hand a little and see if it starts better. If it does then you know right off the bat not enough fuel to much air which is what I think is your problem along with tight valves.
Alleyoop

[sprocket]

I agree the valves sound tight to me...

[jhbietz]

A compression test would be a good place to start. If you don't have access to a comprehension tester I agree you should check the valve clearance. I have often had to adjust the valves a second time after break in when installing a BBK.

[erikegbert]

Thanks you guys seem to know what your talking about. Im going to attempt the valves this weekend if i get a chance. What would be the correct clearence so i can get the feeler guages in the correct size? As for the K&N style filter...I had took that off and put the original air box back on and it didnt help the problem at all. Im going with the valves...the guy who did this for me told me the valves dont need to be readjusted but if i wanted them done he would charge me again....I think im just going to do my own work on this thing now..

[cometman]

To adjust the valves, remove the valve cover and turn engine over until piston reaches TDC top dead center, you can do this by putting a socket on the flywheel and turning it until you see the markings or holes on the cam chain sprocket, they should be even with the head, at this point both valves should be completely closed, if you grab the rocker arms, you should be able to jiggle them a minute amount, if they do not move, they are too tight. I adjusted mine to .004 and they seem fine, not sure what the tech manual suggests.
Tom Cometman

[sprocket]

I like to do the exhaust at .005. Mostly habit, but a few years ago I studied valve temperatures in racing engines and the exhaust valves were always hotter and therefore expanded just a bit more...