Baadd Vibration

europorsche914 · #1 09-15-2008, 12:52 PM

Hi had my HT kit installed for 2 months and have put 600 miles on it. It is a non roller bearing engine. I normally cruise at 18 mph and dont drive too too often at the vibration barrier. Just the other day I was riding it and it started to vibrate real bad at 18 mph and sounded real rough. I always run the motor with 20:1 premix and have no idea what happened. I shined a flash light into the spark plug whole and the piston walls are still shiny and smooth. Could there be somethin wrong with the bottom end? Thanks (long time reader first time writer)

FileStyle · #2 09-15-2008, 01:26 PM

check your mounting studs where they bolt to the bike! and if you hav'nt done so already replace the studs with some grade 5-8 bolts. this has happened to me before also and I found a broken stud on the rear motor mount!

**Dave31** · #3 09-15-2008, 02:01 PM

Welcome to the forum euro914, glad you joined us

Yes, I would check your mounts first and then go from there. Keep us posted

velardejose · #4 09-15-2008, 02:35 PM

Hi
About that 'vibration barrier' (my bike does it too when floored in flat ground)
At what RPM does it happen?
Why does it happen?
I know these are cheap engines that last a lot when stock, would it be worthwhile to balance the botom end?
Thanks in advance

europorsche914 · #5 09-15-2008, 02:46 PM

mounts are solid and i adjusted the clutch and the vibration was still there

**Bikeguy Joe** · #6 09-15-2008, 03:19 PM

Does it do it if you go fast enough to get it to vibrate, then pull in the clutch and kill the engine?

**Bikeguy Joe** · #7 09-15-2008, 03:21 PM

BTW- go to 24:1 mixture, you'll like that.

europorsche914 · #8 09-16-2008, 12:52 PM

no it doesnt vibrate at that speed with engine off. I took the motor off and tore the top end apart and there was no evidence of any damage. When i move the piston (and therefore the entire bottom end) I do not notice any appreciable slop in vertical movement so i dont think there is anything wrong with the bushings. While its apart I am goin to do some porting to the intake and exhaust ports on the cylinder (1.1" from top for exhaust and drop .25" on intake (I think these are correct)). I wonder it it may have been misfiring due to all the carbon buildup in the cyl... I am running the b6 NGK. After seeing the cylinder I will be leaning my mix out a little...
Are my porting numbers correct?
Thanks for everyones help so far -Justin

europorsche914 · #9 09-18-2008, 10:03 AM

Finished porting motor and reinstalled it. No vibration now and engine runs so much smoother after porting and makes alot more power than before.

**Dave31** · #10 09-18-2008, 01:36 PM

Quote:

Originally Posted by europorsche914

Finished porting motor and reinstalled it. No vibration now and engine runs so much smoother after porting and makes alot more power than before.