SBP kit chain tightness possibly causing engine shutdown

Yes! Too tight a chain will also damage things if you DO manage to get it going.
Recheck your installation and get the chains sorted out correctly.

i had to re;engineer my SBP shifter kit to get the clearance an adjustment needed
frankly it was a pain in the ... (yes my engine is a 5/8th shaft engine)

anyway i'm guessing you are talking about the short
chain from the 4G drive to the jack shaft gear as maniac said it SHOULDN'T be that
tight so you need to make a new length of chain add 1 link

in saying that it would be easier to judge an give advice if you could add picture/s

Well this is why we always advise new people to make sure their engine runs and is at least half way tuned before installing the Shifter Kit.

But no a tight chain won't cause this:

" i am able to start it but it doesnt want to stay on unless i am 100% open throttle."

That has nothing to do with the drive system. You generally want your chains fairly snug. They would have to be really tight to damage things - bearings, chains, sprockets.

Indeed please post pictures.


Lastly, have you contacted Jim at SBP? I have forwarded this thread to him. We do provide customer support.

ajoh said:

i had to re;engineer my SBP shifter kit to get the clearance an adjustment needed
frankly it was a pain in the ... (yes my engine is a 5/8th shaft engine)

Click to expand...

I had the same problem with my SBP + 4G setup early on, but I simply switched to halflink chain to solve it.
Initially I needed 12.5 full links, but 25 half links worked better. After a couple years I switched the 17T jackshaft input to 18T and now run 26 half links. Running full link chain is impossible with my 11T->18T combo (always way too loose), but halflink chain does the job great. It was very tight with engine mounted as far back on mount as possible, but it ran awesome! The chain has since stretched/sprockets wore in a bit and now it has perfect tension. Over 2K miles on this setup.

anyway i'm guessing you are talking about the short
chain from the 4G drive to the jack shaft gear as maniac said it SHOULDN'T be that
tight so you need to make a new length of chain add 1 link

Click to expand...

I don't think OP is even talking abut a 4-stroke setup tho, as the SBP shift kit was originally designed for the chinagirl and is so used on many many more setups here than our SBP+4G rigs. Also, adding a link may not help at all when using a full link chain due to the nature of full link chain and certain sprocket sizes and distances between them.

Jerrycurljuice said:

So today was the first day i started my MB. The problem is it is ridiculously hard to start it! It feels as if the chain will not let it start with me pedaling as hard as i can. Then once ive turned green and became the HULK i am able to start it but it doesnt want to stay on unless i am 100% open throttle. If i stop it, it stops.. So my newbie question is how tight should the chain be coming from the engine to the jack shaft on a SBP kit. Mine currently feels so tight that you would think its welded together. I know it is suppose to be "tight" but yeah. Can this be possibly causing my engine shutdown due to the inability to move freely?

Click to expand...

The chain being very tight will definitely increase drag on the engine during geared operation and likely shorten the life of your jackshaft and jackshaft bearings, but as I also have run with an extremely tight primary chain without any adverse engine performance, I'm inclined to agree with Pablo that your problem isn't related to the jackshaft. My reasoning, assuming you have a 2-stroke with SBP kit:

With clutch lever locked on a 2-stroke kit, the jackshaft tension should have no effect on whether the engine runs or not. Remove sparkplug and check engine crankshaft for excessive tightness. Also check the "bucking bar", aka the clutch actuator pin in the cover underneath the clutch actuator lever. This pin/dowel must be greased regularly because if it gets dry, will reduce any freewheel ability. You will probably need to start the engine with bike on a stand; with rear wheel off the ground to make sure the engine runs okay before blaming it on the drivetrain.

Also, double check that all chains are straight and track true. Pics will definitely help!

(note cut an pasted from the other thread i posted in posted here to for more people to see if my other post isn't seen)

time for me to eat crow be a man an admit i was wrong

Ghost0 (i'm guessing you're the sickbikeparts man) let me say i'm so very sorry
for what i said about the 4stroke shifter jack shaft kit i finally work out my
problem was with the shifter kit but the chain i was using i was using the chain
that came with the engine kit

damn i feel dumb i didn't realize this mistake untill i read The Aleman say something
about "bmx" or "single speed" bike chain is the same pitch as 415 when it clicked
that's what the install manual was pointing at (as it doesn't exactly say still my fault)

anyway i just wanted to stand up an admit my mistake an say sorry sick bike parts