engine vibration

[petejw]

ive swapped over engines and fitted
a 3x1 with a mechanical advance and 2h7 tci
from my 5n5 engine that was fitted with a 4ro tci,
the bike pulls hard to redline but the engine vibrates
pretty bad from around 4000 rpm to redline,
any thoughts on what could be causing it,
the engine has been tuned and synced, the mech adv
is free, the engine idles well and runs well till the vibration
kicks in.
tia.

[BA80]

Check your engine mounts Pete. The engine is probably touching the frame somewhere.

[ViperRon]

Pete if you can not find any place the engine is touching the frame try running the bike in neutral and use a Stethoscope if you do not have one small piece of PVC pipe on the engine in several places may help to isolate the noise. You may find its exaust or something else vibrating.

[DGXSER]

I find that on my current SH with the exhaust system on it, right about 4k it starts to put off more vibration. I can hear it in the exhaust tone as well. It seems to lessen alot above 5k.

[DAVINCI]

Pete, have you checked the timing with a light? You may have too much initial advance??

[petejw]

sorry havent been on for a few days,
thanx for the replys,
the vibration is pretty full on, in that i cant
ride the bike after it hits 4000rpm, it feels like
something is out of ballance, the clutch was slipping
so i tore into that hoping something might be wrong there,
replaced the clutch basket and insides, it helped a little
but not much, the other thing i was thinking it could be
the rotor, but the bikes charging fine i cant see what could
go wrong with that.

greg, i resleeved the engine mounts with an inner tube,
the mounts are in tite there not hitting the frame, i could remove
the inner tube and put the mounts back in, but when it was mounted in the other bike i could still feel the vibration just not as bad.

randy, ive set the initial timing at 10 degrees, i could drop it back to
5, but its not pinging so id think that should be fine.

don, was thinking the same thing i had a 4 -1 jardine on it, then swapped
it out with a 4-2-1, the problem is the same.

ron, ive got a stethoscope but the engine isnt making a noise as such
and the vibration doesnt come into it till 4000rpm other than that it idles
nicely.

[James England]

What do you mean by "inner tube"? Surely not an inner tube from a wheel?

[ViperRon]

Pete I have a hard time trying to visualize the vibration. Can you duplicate it sitting on the stand.

If it does it sitting on the stand out of gear its the engine and typically the balance is threw the crank shaft. The only things that I know can change the balance is rods or pistons or a differential of power. If there is a delay in firing of cylinders or severe difference in power from a cylinder that can cause a vibration that will increase with rpm. If no rods or piston changes and you do not have noise or nock at low rpm then I'd try an unothadox method and run for a few seconds on only 2 cylinders then switch to the other 2 and see if that identifies a difference or starting point.

If it only does it in gear with the rear wheel spinning you have a different direction to go.

[petejw]

What do you mean by "inner tube"? Surely not an inner tube from a wheel?

hi james,
thats exactly what i mean, i used a bicycle inner tube
slid over the worn rubber engine mounts, sprayed some
silicone over it and slid them into the engine, ive done it before
with good results, do u see a problem with this?

hey ron, the whole bike shudders under load, from around
3500-4000rpm
it also does the same thing in neutral but not as bad,
ive never felt anything like it before, the bike has power
and making no noises or knocks, thats y i thought the crank
and bearings should be ok.

[James England]

hi james,
thats exactly what i mean, i used a bicycle inner tube
slid over the worn rubber engine mounts, sprayed some
silicone over it and slid them into the engine, ive done it before
with good results, do u see a problem with this?

Right. I thought you meant that you had entirely replaced the OEM mounts with inner tube (maybe rolled up). No, I don't think this will be the cause of your vibration then.

Mostly, I've found the vibes usually are most noticeable at 4,000rpm+ on these bikes, sometimes enough to whiten fingers.

Have you checked the pickup wires, plugs, coils etc? I wonder of you have a misfire at 4,000rpm+ ?

[petejw]

Right. I thought you meant that you had entirely replaced the OEM mounts with inner tube (maybe rolled up). No, I don't think this will be the cause of your vibration then.

Mostly, I've found the vibes usually are most noticeable at 4,000rpm+ on these bikes, sometimes enough to whiten fingers.

Have you checked the pickup wires, plugs, coils etc? I wonder of you have a misfire at 4,000rpm+ ?

lol thats funny, no i still used the original rubber mounts,

my other engines have had the vibration at 4000rpm, but this
is much more, the whole bike shakes to the extent u cant ride it,
the engine isnt missing and the plugs look fine, it idles fine too,
im going to check the rotor out, but i cant see that being a problem.

[ViperRon]

Pete as James had mentioned that is where I was going with this because if you do not hear a knock and no noise it has to be a power differential. If it was a fuel problem it seems like it would be seen sooner. That is why I thought trying to run on 2 cylinders at a time might tell which circuit to look in. After you identify if its 1 & 4 or 2 & 3 you can further make sure ist not a fuel problem by switching electronics and see if it follows the electronics. I know shade tree approach but its really hard to isolate without an analizer to look at power output. I can't even think at 4000K anymore.

[BA80]

Do you know any history on this engine Pete? Did you take it out of another running bike or did you get it not running? What I'm getting at is did the vibration exist before you got it? If the vibration is as bad as you say it wouldn't have been ridden before I would think.

If it seems like a balance issue The first thing I would do is check everything I bolted to the crankshaft. Make sure it's not something I did. These engines are internaly balanced so unless the crankshaft is way out of balance, which is highly unlikely unless the engine was rebuilt and the balance counter weights on the crank were messed with, it's going to be something external. I would think most likely the rotor for the alternator.

Just thinking out loud, so to speak.

[petejw]

Pete as James had mentioned that is where I was going with this because if you do not hear a knock and no noise it has to be a power differential. If it was a fuel problem it seems like it would be seen sooner. That is why I thought trying to run on 2 cylinders at a time might tell which circuit to look in. After you identify if its 1 & 4 or 2 & 3 you can further make sure ist not a fuel problem by switching electronics and see if it follows the electronics. I know shade tree approach but its really hard to isolate without an analizer to look at power output. I can't even think at 4000K anymore.

i can give it a go ron,
cant hurt hey.

its improved slightly after i changed out the clutch,
i know there are some roller bearings fitted near the transmission
was thinking if those bearings might have collapsed it could
cause the problem.

[petejw]

Do you know any history on this engine Pete? Did you take it out of another running bike or did you get it not running? What I'm getting at is did the vibration exist before you got it? If the vibration is as bad as you say it wouldn't have been ridden before I would think.

If it seems like a balance issue The first thing I would do is check everything I bolted to the crankshaft. Make sure it's not something I did. These engines are internaly balanced so unless the crankshaft is way out of balance, which is highly unlikely unless the engine was rebuilt and the balance counter weights on the crank were messed with, it's going to be something external. I would think most likely the rotor for the alternator.

Just thinking out loud, so to speak.

greg, it was a parts bike i picked up that had been sitting for a cpl
of years, was originally fitted in a standard, the po had butchered it
a fair bit tho, trashed the wiring loom, wrong length spark plugs fitted
cam caps fitted in wrong order and facing wrong way, looks like
he'd been in the clutch before as well, so who knows what else
he had done to it,

anyway i put it all together and
got it running, it had a vibration when i rode it, but nothing like it
has now since i swapped it out and sleeved the rubber mounts the
vibration was way more.

i was thinking the same, the crank shaft is drilled for balance, so its
not like a weight has flung off and caused it to be out of balance,
im going to check the rotor tomorrow, but i cant see anything that
could go wrong with it, if it was running 'crooked' then i would think
it would rub/hit the stator, theres no oil leaking out from the crank
seals.