75 RD350B Vibration

[rd350mississauga]

I have a 75' RD350B US Spec. The front end vibrates so much after 5K RPM; that my hands and elbows hurt. Low end of the RPM band is fine. I bought it this way 3 years back but was too excited to care then  This is what I did:

1. It was missing a rear engine mounting bolt. I bought an OEM piece off a part-out bike hoping it would fix the issue, but it didnt affect the vibration even a tiny bit.
2. It was also missing the rubber dampers in the cylinder head/fin. I bought the whole kit off yambits, installed it and again, it didnt help 1 bit.

It came with a DG pipe, 210 main jets, and uni filter, rest is stock. How can I get rid of this vibration?

[kramdua]

mine vibrates at around 5k rpm but not nearly as bad as you say yours is. does it have good rubber bushings on your handlebar risers?

[m in sc]

make sure  all the motor mount bolts are tight, particularly the front mounts

[Striker1423]

Handlebar bushings, foot peg bushings. Most of these are blown out and no good. Worth a look. Tighten motor mount bolts for sure! Also, a set of bar end weights really helps. The heavier the better!

[1976RD400C]

Exhaust pipe rattling?

[m in sc]

the only time i ever had oen vibrate really badly, was 1 time i had one that once carb slide pin back out and the RH carb hung wide open, and it actually twisted the crank as i couldnt get it to shut down. not saying thats what happened here, but after everything else is exhausted, nut and bolt, timing, carb synch, etc, that might be worth a look.

[rd350mississauga]

Thank you all for the kind comments

@

mine vibrates at around 5k rpm but not nearly as bad as you say yours is. does it have good rubber bushings on your handlebar risers?

Ill definitely check this.

make sure  all the motor mount bolts are tight, particularly the front mounts

Yes, they are tight. Thank you for the suggestion.

Handlebar bushings, foot peg bushings. Most of these are blown out and no good. Worth a look. Tighten motor mount bolts for sure! Also, a set of bar end weights really helps. The heavier the better!

I have to check the handlebar bushings. I just installed footpeg bushings from yambits.

Exhaust pipe rattling?

Theres no rattle as such, I checked it today. But the exhaust gasket (the connection between the cylinder barrel and the pipe) is missing and there seems to be a sealant instead. Next thing on my todo list is to order the diamond shaped gasket.

Also the bolt support (near the footpeg) for the DG is missing a grommet when I checked the parts diagram, but its snug. Ordering the grommet too.

Handlebar bushings, foot peg bushings. Most of these are blown out and no good. Worth a look. Tighten motor mount bolts for sure! Also, a set of bar end weights really helps. The heavier the better!

Will try this for sure

the only time i ever had oen vibrate really badly, was 1 time i had one that once carb slide pin back out and the RH carb hung wide open, and it actually twisted the crank as i couldnt get it to shut down. not saying thats what happened here, but after everything else is exhausted, nut and bolt, timing, carb synch, etc, that might be worth a look.

The pin is good. I know what you mean. Happened to a friend of mine, but in his case, he just switched it off. Youre running the HPI right? Im running it too, so the keys are basically useless on mine, since I havent figured out how to ground the HPI onto the key system, I use the engine kill switch, which is also in reverse. On is Off and Off is On.

[pdxjim]

Mismatched pistons?
Spun crank?

Just guessing here, as every Yamaha twin I've ridden has been smooth as glass especially at higher rpms.

[m in sc]

mine ran on long before the cdis were available, just fyi. they can do that even with points. this was close to 20 yrs ago.

what im saying is, it may have happened before you got the bike.

[RustyRD]

double check carb sync, as Mark stated earlier. I have dealt with this myself. Out of sync carbs can produce vibration.

[kramdua]

i recall now back around 1980 my rd350b really had a vibration i had ignored. actually the frame tabs for the front engine mount had broken and i had to get them welded back on. i am not for sure but i think i still ignored the vibration because i never had the engine apart.