ProMod jackshaft bending

[chazdaddy]

I have bent the alum plate a couple times and wondering if anyone else has this problem. I ride my DB30 pretty hard I suppose, because I have also busted the chords on the tires too.

The 1st time I noticed it was bent, I removed it from the engine and straightened it in a vise. The alum plate is fairly soft and easy to straighten, but a lot of trouble to disassemble/ reassemble.

It will bend if the chain is too tight, and tends to bend towards the engine when the chassis flexes (I guess?). The last time the chain was too loose and came off which bent it approx 1/2" to the inside. I have a sprocket protector that works really well keeping a loose chain on the rear sprocket, but the chain will come off if really loose.

This last fix I left the jackshaft on the engine and used a piece of muffler pipe with enough ID to fit over the bearing housing. Then I pried it back into place, using the pipe as a lever. I was pretty proud of the fix, was fast and easy, fixed it perfect.

I love my ProMod jackshaft. I think it is one of the best options for your Baja Doodlebug if you want to keep the 97cc engine. If the jackshaft didn't bend, would probably break something else more expensive or harder to fix. So, OK with me if bends from time to time.

Anyone else have this issue? :shrug:

 

[Camjamsdad]

I have two, one on my fast clone and the other on a stock 97cc. Neither has bent but you can feel it flex if you push on it. I also made my primary chains as short as possible so the plate is as short as I can make it. Maybe you could add some gussets to strengthen it?

What's your thinking about the thin steel TAV back plate? I suspect it would also have flex. I'll find out soon enough because it's the next mod up for my speed bike

 

[greaser_monkey]

I have a gtc jackshaft, which to my knowledge is the same as the promod one (gtc makes them for promod)? Never had it bend. I run my primary chain pretty loose, never had it come off. Too tight and the clutch won't engage smoothly at all. I run a tensioner on my secondary chain.

 

[chazdaddy]

I run the primary chain pretty loose too, not having problems with that part of jackshaft. A chain tensioner is a good idea, but I will probably not add one. With my chain guide, I can ride all day and not have any problems. Appears, just need to tighten chain a little from time to time.

When I 1st added the jackshaft, I removed the chain roller and worked OK for awhile. Later, as I rode more/ faster the chain started to come off pretty often. So, I tried one with the chain guide on the rear sprocket only, no roller chain guide. The other DB30 I put the stock roller chain guide back on without the sprocket chain guide.

They both work about as well. I like the chain guide a little better, seems to protect the chain more, chain stays in better shape. With the roller, the chain dries out faster, is more exposed to dust/ dirt.

I don't know about the Baja jackshaft that comes on the MB160/ 200, but understand they have some weak areas. They look like they would flex.

pic of chain guide on a street set-up: