Insane Vibration

[LabDude661]

I have been searching the forum for days now looking for an answer and forgive me if I missed a post that already discusses the issue. I got a 70cc HT from boygofast. Everything looks fine and runs fine except I have been getting insane amounts of vibration. I'm running a 44t sproket and I can only get to like 25 mph before the handlebars want to buzz out of my hands. The highest comfortable cruising speed I've gotten is about 21 mph. Was I just naive to belive that this thing would do 35 out of the box or is the vibration keeping me from going top speed? I really don't need to go much faster but it would be fun . I used an old innnertuber around the frame on the mounts and I loaded the handlebars with lead weights and I still can't break about 26 mph without pain from the vibration. I've seen a few little rubber engine mounts that might work but I wanted to know if anyone else is having this same problem. Everyone on here is talking about 35 40 mph and I'll just say it... I'm jealous!!! :yuck:

 

[Skyliner70cc]

If you want 35-40 mph, consider a scooter. I have no problem hitting max rpms on my BGF engine without an vibration issues. Some bike frames and mount setups are more prone to vibration than others.

 

[andyinchville1]

HI,

Assuming your engine is running properly (not missing etc....) and is securely/properly fastened to the frame, the best thing you can do to reduce vibrations and increase speed is to get a smaller rear sprocket....It'll kill 2 birds with 1 stone....Try it you'll like it! ;-)

Hope this helps.

Andrew

 

[Skyliner70cc]

Is you bike an old Huffy by chance? I had a Huffy bike that vibrated like crazy and I blamed it on the engine. I swapped engines and didn't help one bit.

 

[LabDude661]

Nope it's a pretty sturdy mountain bike. I'm going to try putting big hunks of car tire on the mounting points to see if that helps. I've been seriously considering getting a smaller sprocket but I want to be sure that the problem won't still be there. I don't want to cut the chain and drop more money on the problem if it's just the bike.

 

[hill climber]

my ht vibrates like crazy too, but i can get 40 plus out of it with the jack shaft and 6 gears. i dont have a tach but am a motorhead and i bet its turnnin 6000-6500 rpm maybe more. it runs smoother at the higher rpm for sure, if you can get the jetting right. by the way when i put my expanshion chamber on it smoothed out considerabley. hill climber

 

[LabDude661]

where do you pick up an expansion chamber, or is it a DIY mod?

 

[Stink Bike]

I was getting a bad vibration at about 30 k's so I cut a spark plug lead in to 1/4 inch lengths and jammed it in between the fins of the motor.Problem solved..... and it reduced the noise.This has been the best and cheapest mod I have done to my motor.

I still get plenty of vibration through my hands.

 

[hill climber]

where do you pick up an expansion chamber, or is it a DIY mod?

it is a diy but works very well, probley doubled the power, its off a 85 suzuki rm 80, i moded the first 8-10 inches and a couple custum bends in the tail pipe before the silencer. sick bike parts has two different models for sale for the ht, one v frame type and a cruiser type. i found them in here just search expantion chamber. there is another guy selling pipes here. no coment on these. hill climber

 

[relaxxx]

My experience has been the faster I run the motor the smoother the ride. I'm on my second frame, a cheap walmart bike with front shocks and I mounted the motor with some tire rubber and it is a very nice ride compared to my first frame. If you want to go faster than 25MPH, definitely get a small sprocket. After running a 36T I'd never consider going back to 44T. I don't understand why they even sell 70cc motors with 44T. Mt 36T climbs hills just as well as the 44T did, if not better!