70cc knock

[mikal]

I installed my 70 airsal yesterday and now there is a loud knocking noise. o-- The noise seems to have a rythym with how far the throttle is open. I cant hear it at louder revs. I took it to my honda dealer and he said that it could be cause the 50cc cooling system is not designed for the 70 and for that they leave some space between the cylinder and the piston, which would create the tapping sound. Also, it sounds like it could be coming from the pipe, but I disregarded that theory because the I thought the sound was just traveling through the pipe from the exhuast port. Any ideas?

[pinkymingeo]

If you're using the "P" plug, change it.

[mikal]

pretty sure that the plug is a br7hs no p. Any other ideas?

[ratboycom]

go to a different heat range, the 7 is too hot its probably preignition that you are hearing

[mikal]

Sorry it is a br9hs. The clicking or knocking or whatever, seems to go away with the revs way up, but then when they come down you can hear the clicking in real fast time for about 3 seconds and then it goes away. Untill the bike goes down to near an idle.

[Zuma-Zuma]

Is something hitting the fan? Is it possible the vario is loose? Kickstarter touching? Stone in the tire? (:) )

[mikal]

The vario is tight, the sound is much louder on the pipe side. I wish it was a stone in the tire, but it does it when I am sitting still. Its a two ring piston, and I wasnt sure which ring went where could that make the noise?

[mikal]

Another thing that was brought to my attention, was that the piston might not have been top dead center when I installed it. Would it find T.D.C. throughout the cycle or could that throw the timing off? Would the timing being off create a tinkering sound?

[Zuma-Zuma]

PIston only goes on the rod. TDC means nothing (unless you have a clearance problem). Tming isn't off either (wouldn't make noise). As long as the rings are indexed on the piston correctly. The gap's of the rings should be at the pins in the ring grooves.

There is a difference between knocking, clicking, and rattling. Does it rattle when NOT moving? Just the motor revving, and the rear brake on?

[mikal]

The best way to describe the sound is if you were to hit the blade of a fan as it is spinning. When I rev the engine it is like it is turning up the speed of the fan, up to the final top speed were you cant hear it anymore. I thought I had placed the rings right over the pin in the groove, but they were so loose fitting around the piston that they could have moved. The piston went into the cylinder quite easily just with me compressing the rings.

[Lennox]

The best way to describe the sound is if you were to hit the blade of a fan as it is spinning. .

why on earth would you do something like that?? :jesta:


did you end up using the stock carb?

[mikal]

For now the stock carb is in effect, with a stock 90 main. I know, I know, 19mm, 19mm,19mm, the mods are endless and the carb will be here soon enough.

[Tommy Wise]

Holy for Christ sakes!!!!! I think you're all reading waaay too much into this! You know all the stupid springs that ar3e around all the cables and what not? Take them all off and I bet vyou they acount for 95% of the noise! contact me if you disagree!!!!!! SUYCKA.,.......

[xraydino]

Don't know what your rambleing about but, I'll disagree.

[~cheap_ride~]

i went thru something similar recently, i started hearing a vibration noise, low rpm , high rpm, didnt matter. the bike was operating fine so i just kept my ears open to see if it got worse or not. I hadnt preformed any mods prior to the noise developing so i was really stuck as to what was making it.

what i found it out to be is the centerstand touches my pipe, granted its not touching that much but enough to periodically make a vibration noise. something to check anyway.

tom

[mikal]

OK this was the problem. The piston was installed upside down. so I think the rings were running against the exhaust port. That is the good news kind of . I pulled the bike apart, reversed the piston, and lost a circlip. Ultimately used an old one cause I could not find the lost one. Well I found its location. Stuck inside the cylinder rubbing against the piston ruining it. LOL or whatever, live and learn. The new piston is in the mail. The few hours that I had with 70cc were enough to get me hooked.

[mikal]

Cheap ride, my stand hits the pipe on my wifes 02 vino.

[xraydino]

Mial, that's a bummer. I've come close to that happening a few times. You can cut your odds of that happening again by 1/2 by installing one of the clips before you even slide the piston on. Put the pin in, then one clip, carefully push the pin back out, then line up the piston to the rod.

[Zuma-Zuma]

Pistons go in backwards, NOT upside down :P

ADD: If you're new at this, take a magic marker, and put an arrow on the new piston facing the exhaust BEFORE removing the old piston. Hold them side to side if you have to. I've used Wiseco's and others, they have an arrow in the casting.

[speedy_scooter]

I'm surprised that it ran with it backwards.

[xraydino]

When I installed my T6 it didn't have an arrow. I had to go through the how tos and try to compare pictures. Even then I scratched my head a few times while tuning thinking that I may have did it backwards. Nothing like doing everything twice to ruin your day. _-_-_-

[Zuma-Zuma]

Doesn't the cut out match the ports, same width??

[Ochlockonee]

Yah, I matched to cutouts to the ports to figure out how the piston is oriented.