Thinking of ordering shift kit and exp. chamber, pros and cons?

[rudyauction509]

Several years ago I had a 49cc bike with the shift kit. I remember that after the first month I had problems with the chain from jackshaft to bottom bracket stretching, breaking and dropping off even when properly oiled.

I just built myself a 66cc bike for backup transportation, and would like to put a shift kit on it, but am wondering if there's a way to avoid those issues. I've been using it lots lately (even more than my truck when the roads are dry) because it's so fun to ride and would like to get some extra hill climbing power and top speed. Anyone else with experience with the shift kit? How does it handle the power? With a good engine will I be able to keep up with 35mph traffic?

Also thinking of either the sbp expansion chamber or the high power CDI. I'm looking for a boost in power (but not revs - shift kit handles top speed). I prefer reliability over raw power as I sometimes ride 100 miles plus in a day. Which of these will be better? Does the CDI actually give more power? And can pipe be tuned for low end torque, with a peak at say 4000 rpm? And what about reliability? I assume the CDI won't effect the reliability of the engine itself, but if there's no real boost in power I'll just carry an extra chinese CDI.

Also need to have some good hill climbing power for going up the south hill, as well as light trail riding (where low speeds and high torque are needed) at Priest Lake in the spring and summer.

I remember gearing my shift kit as low as possible, with a ~50 and ~30 tooth on the bottom bracket, so that the slowest gear was like 5mph top speed yet it still didn't have much torque. I don't plan to do this again but want to make sure that I'll have better acceleration with it set up correctly.

 

[cannonball2]

Im pleased with my upgrade CDI. I noticed improved running. I am running a stock engine. A big advantage over the stock CDI is you are running a decent M/C coil if nothing else. The coil in the stock unit is known to be undersized and not serviceable. I would take the time to develop a well running stock engine first, break in, jetting , etc. before modding. That way you have a base line to begin with.
My opinion on the pipe for a stock engine is its probably over kill and can be an issue to mount, though the SBP pipe is a good one. Adding length to a decent stock mufflers header and a longer intake will add bottom/midrange which I think is what you are after. Very useful on a shifter.

 

[KCvale]

Several years ago I had a 49cc bike with the shift kit. I remember that after the first month I had problems with the chain from jackshaft to bottom bracket stretching, breaking and dropping off even when properly oiled.

Several things can cause that but if properly assembled, aligned and secured they work great though you can use KMC 710 chain for there, it's is 410 all 1/2 link chain and it's tough stuff.
The bonus is it's all 1/2 links, no mater link, just a cotter pin to join the ends so getting the length right is easier.

How does it handle the power?
With a good engine will I be able to keep up with 35mph traffic?

That depends entirely on what gearing you have on the back wheel.
Personally I dislike using any derailleur with a performance engine, your chain line is only straight in 1 gear and even HD 7-speed will snap with a bad shift.
For me nothing beats a 3-speed hub shifter, you have the same top and bottom gear ratio, just in 3 steps and it's a fixed sprocket you can align to.

As for speed, as long as you don't gear it too low 35MPH is easy and what I usually ride at ;-}

Also thinking of either the sbp expansion chamber or the high power CDI. I'm looking for a boost in power (but not revs - shift kit handles top speed).

I haven't tried any aftermarket CDI's, I rewire the Mag to CDI with double insulated 16g wire and plop an NGK 5944 (BPR7HIX) Iridium plug in it which gives you a bit a of boost.

An expansion chamber is great performance add-on.
Some work much better than others but I usually the SBP pipe.
As mentioned it is a bit unruly to install but gives you quite a wallop of power increase.

Here is a recent build with all the above except the 3-speed.

Even with the fat tires it'll run with 35MPH traffic.

Hope that helps.

 

[rudyauction509]

Several things can cause that but if properly assembled, aligned and secured they work great though you can use KMC 710 chain for there, it's is 410 all 1/2 link chain and it's tough stuff.
The bonus is it's all 1/2 links, no mater link, just a cotter pin to join the ends so getting the length right is easier.


That depends entirely on what gearing you have on the back wheel.
Personally I dislike using any derailleur with a performance engine, your chain line is only straight in 1 gear and even HD 7-speed will snap with a bad shift.
For me nothing beats a 3-speed hub shifter, you have the same top and bottom gear ratio, just in 3 steps and it's a fixed sprocket you can align to.

As for speed, as long as you don't gear it too low 35MPH is easy and what I usually ride at ;-}


I haven't tried any aftermarket CDI's, I rewire the Mag to CDI with double insulated 16g wire and plop an NGK 5944 (BPR7HIX) Iridium plug in it which gives you a bit a of boost.

An expansion chamber is great performance add-on.
Some work much better than others but I usually the SBP pipe.
As mentioned it is a bit unruly to install but gives you quite a wallop of power increase.

Here is a recent build with all the above except the 3-speed.

Even with the fat tires it'll run with 35MPH traffic.

Hope that helps.

Thanks for all the great info! I think I may take that $70 for the cdi or pipe and use it for a 3 speed hub. The only problem is that my rim uses more spokes than normal, it's 29" and has 10 pairs per side instead of 9. I'll go to a bike shop today and see what I can do.

Side note, are those hubs durable enough for the engines? I used one for a 500 watt electric bike but that didn't have even close to the power these engines have.

 

[rudyauction509]

What about a 5 speed hub?

 

[rudyauction509]

OK - I dropped by a bike shop today, getting a 29" 3 speed hub is going to run me near $300. I'm looking for one on craigslist now (if you have one let me know I'll buy it). I think it'll be worth it though. I'm going to leave the derailleur on but set it up to line up with the sprocket, so it can pick up the slack when the chain stretches. Also on trips I can have a couple different sprockets for the 3 speed hub, allowing me to easily change overall gear ratios for speed or hill climbing.

Also I think I'm going to jump on the expansion chamber, my engine could use a power boost, with my new 29" wheels I'm having trouble getting up to speed.

 

[maniac57]

While I have never run a shift kit, I do have a 5speed derailleur/jackshaft bike and I run both a pipe and aftermarket cdi.
The CDI (lightning hd) is a big improvement in engine manners with much better low end response and FAR less "popping" and missing at low rpm's. It pulls cleaner from much lower rpm and feels noticably nicer to ride. Overall power is boosted very little if any. Maybe a few more rpm on top, but the better spark is worthwhile for anyone looking for a better running chinadoll.
The pipe also helps low end rpm quite a bit and depending what pipe you get and how it's tuned, can make a HUGE difference in power and low end torque. Do your homework and it's the single biggest power gain you can bolt on. Period.
As far as the drivetrain, I have to agree with KC. The derailleur setup is simply too fragile for daily transportation. Even when I'm extremely careful, I still get occasional chain jumps which can be devastating under power! Go with the internal 3spd hub. The 5 speeds and NuVinci types are still a bit fragile, but some people run them. I'd stick with the proven 3spd were I to rebuild it tomorrow.

 

[rudyauction509]

While I have never run a shift kit, I do have a 5speed derailleur/jackshaft bike and I run both a pipe and aftermarket cdi.
The CDI (lightning hd) is a big improvement in engine manners with much better low end response and FAR less "popping" and missing at low rpm's. It pulls cleaner from much lower rpm and feels noticably nicer to ride. Overall power is boosted very little if any. Maybe a few more rpm on top, but the better spark is worthwhile for anyone looking for a better running chinadoll.
The pipe also helps low end rpm quite a bit and depending what pipe you get and how it's tuned, can make a HUGE difference in power and low end torque. Do your homework and it's the single biggest power gain you can bolt on. Period.
As far as the drivetrain, I have to agree with KC. The derailleur setup is simply too fragile for daily transportation. Even when I'm extremely careful, I still get occasional chain jumps which can be devastating under power! Go with the internal 3spd hub. The 5 speeds and NuVinci types are still a bit fragile, but some people run them. I'd stick with the proven 3spd were I to rebuild it tomorrow.

Thanks, pipe it is. I'm going to grab the sbp pipe since it's got good reviews and is tunable. Also I may have found a good 3 speed hub, I'll just have to put it on the 29" wheel I already have. Hopefully the spokes are the right length.

 

[mapbike]

I don't use a shift kit but I do recommend the SBP pipe for good low to medium rpm power increase over a stock exhaust, I don't want to start a debate about the after market cdi, but I can say I've tried all of them accept the latest Jaguar version and with testing rpm potential and using GPS to monitor top speed and speed start to finish climbing hills and even doing marked off distance runs to see what total acceleration was, I came to a solid fact based conclusion on all my bikes in regards to the HD cdi the standard jaguar set up and the rocket cdi....

None of them showed any gains over a stock unit and actually two of them showed losses compared to the stock cdi.

My advice is don't waist your money on snake oil but instead invest in a RT carb from a forum vendor, get a 6cc Fred Head on your engine for better cooling, tune the carb properly,make sure ports are debuted in engines cylinder, and you'll have what you're looking for when gearing is right.

For what the cdi will cost you can have a Fred Head and good RT carb and it will for sure be a help, the cdi in my opinion and experience offers no gains that's you will notice.

 

[KCvale]

What about a 5 speed hub?

I haven't used a 5-speed internal but Strumey Archer has an HD 5-speed with different brake options like a band brake that should hold up.

What kind of rear wheel drop-outs do you have?
Pictures of your bike would make helping easier (hint hint)

If it's horizontal dropout no need to keep the tensioner, you can just move the wheel back.
Otherwise you will need a different tensioner because you want to run HD KMC 410 single speed chain and it won't run smooth through the thin 7-speed chains derailleur housing very well depending the make.

Since it's a 7-speed bike you should have at least V-brake bosses on the frame but if you have a rear disc get the hub that will take the disc.

If you have neither get a band brake hub because a coaster brake is useless on a shifter, your pedals spin free back pedaling.

It's OK if the hub has a coaster brake, the venerable low cost Shimano Nexus 3-speed hub has one and the hubs with controller are cheap, ~$50, but ya, you'll pay ~$100-$150 to get it laced in perfect with good strong new spokes on a 29" wheel.

As for Nexus 3-speed hub reliability I haven't been able to break one yet with the same power that shreds Nu-Vinci's and the occasional derailleur hubs.

As for high compression heads you need to keep one very important thing in mind, more compression means harder to start, and with a shift kit you don't have bike momentum to help you.

I can't even start this newest shifter with the gasbike HP kit with high compression head without being too winded and sore to even ride the thing.
That is nothing special, there are a LOT of things I can't do anymore hehe ;-}

No more performance upgrades for this thing and it is going to take a competent shifter to ride it or it will shred that drive too, but I just couldn't afford to properly swap out the awesome back wheel to an internal.

Again, derailleurs will work and most builds are, they just aren't as reliable and smooth as internal shift if it's feasible.

I suggest you just concentrate on the drive train and get an NGK 5944 (BPR7HIX) Iridium spark plug and go from there.

Both the NGK 5111 (BP7HS) standard plug and the Iridium are a bit longer than all the stock plugs which gives you a touch more compression itself, the Iridium plug tip just gives a bit better spark I think, there is no gapping them, and it should last the life of your engine.

For ~$10 to add a bit of both what well over $100 worth of parts will do it's sure a bargain.

Want more power?
Expansion chamber, easy to add later ;-}

 

[mapbike]

Great info KC....

Thats a very nice looking bike.

 

[rudyauction509]

Got shift kit and sbp chamber in the mail, and wanted ad up on craigslist for 3 speed hub. Should be here Wednesday. Hopefully everything works.

 

[mapbike]

Got shift kit and sbp chamber in the mail, and wanted ad up on craigslist for 3 speed hub. Should be here Wednesday. Hopefully everything works.

best wishes on the new setup, ill be looking forward to seeing how it all works out for you.

 

[KCvale]

Should be cool, just don't forget to put a C or V brake on the back as the coaster brake will be useless.

 

[mapbike]

Should be cool, just don't forget to put a C or V brake on the back as the coaster brake will be useless.

Are the coaster brakes in the 3 speed hubs that bad KC?

I don't use one myself, I do have three of them I have thought about using at some point in the future maybe.

The reason I ask is because i have rear Coaster hubs on three of my bike and they work great, two of them are Shimano CB -E110 hubs and I have excellent braking with them along with using a front brake, never had any brake fade issues and I can lock up the rear wheel at 30+mph if I wanted to.

Since the OP is using a 3 speed hub and since you have a lot of experience with them I just thought i'd ask if the brakes in those hubs are just not as good as a standard single speed coaster hub such as the Shimano CB -E110.

I do take mine apart and pack with plenty of good High Tack Red Grease before I ever run them, so that might help them out some, but they do a great job of braking on my bikes.

 

[rudyauction509]

With the shift kit you can't pedal back to use coaster brake because of freewheel.

 

[mapbike]

With the shift kit you can't pedal back to use coaster brake because of freewheel.

thats right, duh....lol....!

Wasnt thinking about that one way bearing on the cranks...


thanks for bringing this point to surface, I had my mind on coater hub and wasnt even considering the shift kit part of the whole thing.

 

[rudyauction509]

thats right, duh....lol....!

wasnt thinking about that one way bearing on the cranks...


thanks for bringing this point to surface, I had my mind on coater hu s and wasnt even onsidering the shift kit part of the whole thing.

FYI I've had very good experiences with coaster brakes on single speeds. They usually last about as long as 10 sets of good rim brake pads and easily lock up the rear wheel when needed.

 

[mapbike]

FYI I've had very good experiences with coaster brakes on single speeds. They usually last about as long as 10 sets of good rim brake pads and easily lock up the rear wheel when needed.

Im also a fan of coaster brake hubs, I have the Shimano CB-E110 hub on a couple of my bikes and they perform excellent, better braking than the V brakes at high speed and Ive yet to have to replace the shoes in one of them so far.

I do take them down and clean the factory grease out and pack them good with High Temp High Tack Red Grease.

Ill personally take a good coaster over a standard Caliper Brake.

one of my bikes has coaster and caliper on the rear and caliper on the front for now and it will stop fairly quick if I need to.

 

[KCvale]

thats right, duh....lol....!
Wasnt thinking about that one way bearing on the cranks...

thanks for bringing this point to surface, I had my mind on coater hub and wasnt even considering the shift kit part of the whole thing.

Hehe, ya, 3-speed coaster brakes are actually quite good if you can pedal backwards and won't get in the way of a shift kit, just useless other than helping to hold your axle in place.

Look at the Shimano or SA 3-speed hub with a band brake, a band works better than a C brake.