Wombat vibration

[JPark]

Somewhere in my readings I ran across mention of vibration problems with the 125 motor and perhaps the associated front motor mount. I'll concede that a bigger piston is going to inherently generate more vibration regardless of how well it is balanced.

Overall, the Hodaka vibe level is hard to complain about on the 90s and 100s. It's there, but easy to disregard and free of the high rpm vibe spike that plagues so many old bikes. So my question is if the 125 has the same serene smoothness, and, if not, is there a fix for it. I've never ridden one so have no opinion yet.

[olddogs]

Somebody at Hodaka thought the early 125 Wombats had too much vibration, so they put a head stay on the second batch of 125s. They called this second batch the 94a The brackets are available and can be retrofitted. This model is easy to spot because they came with blinkers

[Dale]

Some of the model 94 Wombats came with an extra engine brace the mounted between the head bolts and the frame. Last I knew, these were still available from Hodaka-Parts. I have one with this brace and one without. Can't tell much if any difference between them.

What will help with vibration is to make sure the engine mounting bolts are tightened while the bolts are centered through the frame holes rather than just letting the bolts fall to the bottom. Put the bolts in place and then shim the motor up so that all weight is removed from the bolts and so that the bolts will slide easily in and out. Now tighten them down and remove the shims.

[matt glascock]

Great tip, Dale. I've not heard that suggested before. I too tried the head-to-frame bracket and didn't notice much difference. Giving it a try.

[olddogs]

I can remember a Dirt Bike magazine test of the Super Rat that recommended tossing the stock motor mount bolts and changing to an American 3/8 bolt to ease vibration. We all ran out and changed to the "stronger" bolts. Never noticed a difference.

[JPark]

Still no answer on whether the difference in vibration over the 100 with the 125 is significant or to be disregarded.

The crank flywheels are decidedly different, with cutouts replacing the holes. On a vertical cylinder you want the balance factor to be high to shift more of the vibes fore and aft, as that is less bothersome. Maybe that's all the material they could get rid of without structural worries.

Without balance factor numbers it's all just speculation. I'm just looking at a 94 that may come my way - tidy and original, but not currently running - and wanting to know what I'm getting into before Bike Acquisition Syndrome takes over.

[viclioce]

Don’t worry too much about it. I put a reeded Combat Wombat motor in a Model 94 frame. I haven’t noticed significant differences in vibration between the 125 and either my Ace B+ or my 99 Road Toad. I think I feel more from the terrain than from motor vibration, any day of the week & twice on Sundays! Buy the bike and restore & enjoy it!!! Victor

[JPark]

Thanks, Victor. I was just a bit concerned because there have been a few vibratory horrors I've run into over the years, usually from a factory's attempts to put ever bigger pistons and such on the same old flywheels that already were pretty perforated from prior 'upgrades'. It looks like Hodaka did it right and made all new parts.

My theory on why the 'shim the motor' trick might work - you need to have a reason to believe - is that it eliminates any preloading of the frame from motor weight so the frame is more evenly compliant to absorbing vibration. The install I did on my 100 was done this way inadvertently and it's smoother than it was before. Nothing to lose.

[Bullfrog]

While I understand the concern - vibration of the 125 cc Hodies is simply not a significant issue. One indicator? How many references can you find about excessive vibration of 125cc Hodies in the history of this Forum? (Answer: not many.) There are no vibration nightmares in your future simply from getting a 125cc Hodaka.

Ed

[Bert44]

I concur with Bullfrogs comment. I don’t recall a thread about vibration issues on this forum. I also don’t think I’ve seen a thread on cracked or broken frame/cycle parts either, which is a sure indication of vibration.
I’ve got a #92 Ace 100 and also a #94 Wombat and I don’t notice any additional vibration, just more power. Compared to my Velo they’re silky smooth.

[dirty_rat]

The only thing I have heard about vibration involved some of the hopped up 125 racers. Some of them would twist the crankshaft a little, causing a lot of vibration. The cure was to spot weld the big end crank pin to the crank halfs so it wouldn't slip/twist.