Can you still use your shifters?

pprwngs

New Member
Joined
May 15, 2018
Messages
1
Likes
0
#1
Hello all! I'm new to the idea of building a gas bike. I'm looking to set it up on a mountain bike, but I would still like to use it without the motor at times. I'm wanting to keep my 21 speed twist shifters. Can someone point me towards some info on how to achieve this? Build threads are also welcomed.

Thanks!
 


Joined
Oct 11, 2016
Messages
135
Likes
15
#2
Yeah you can do this no problem, adding an engine doesn't mess with the bicycle gears.

The only problem is that twist shifters are horrible! You won't have anywhere to put them on your bike. Some people throw away the front shifter and but the rear shifter upside down on the left side of the handlebar. It's much better to change to thumb shifters instead.
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,239
Likes
545
#3
I still use the front and rear gears, allowing me to pedal along with the engine from start-up to very nearly it's top speed, and have a 30T granny ring so that I can get up hills even if the engine breaks down or runs out of fuel.
However the chain and some of the clutch parts will be turning any time the rear wheel is turning because of the fact that the left hand sprocket on the rear wheel is fixed not freewheeling. This isn't too bad, especially if you have a smooth running chain, no tight angle around the tensioner pulley whatsit, and a comparatively small rear sprocket (mine is currently 42T).

Now, personally, since the twist throttle is a bit chunky I decided to put both the shifters on the left hand side. I changed the front shifter to a SRAM one that uses two thumb buttons rather than thumb and forefinger, and I changed the rear shifter to a Shimano compatible gripshift (inverted) so that I can operate both with the same hand. :)

 

crassius

Well-Known Member
Joined
Jul 23, 2012
Messages
4,580
Likes
695
#5
I like cruisers for comfort, but I replaced bars to get them higher and shorter - used a dogbone for shifter even though I have only shifted gears maybe once in 5 years.

shifter.jpg


on a mntn bike I built, there was room for both used for 21 speed

shifters.jpg
 

KCvale

Motorized Bicycle Vendor
Joined
Apr 18, 2010
Messages
3,517
Likes
493
#6
I like cruisers for comfort, but I replaced bars to get them higher and shorter - used a dogbone for shifter even though I have only shifted gears maybe once in 5 years.

on a mntn bike I built, there was room for both used for 21 speed

View attachment 81831
Just because there is room for a front derailleur doesn't mean you should install one.
I remove it to free up space and UN-complicate the bars.
Just put the front chain on the sprocket you want.
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,239
Likes
545
#7
Just because there is room for a front derailleur doesn't mean you should install one.
I remove it to free up space and UN-complicate the bars.
Just put the front chain on the sprocket you want.
What happens when you get beyond the speed where you can pedal effectively using that gear? Do you have to pull over, stop, get off the bike and manually move the chain up onto the next gear? Doesn't that make it difficult to get going again?
 

Frankenstein

Well-Known Member
Joined
Jun 24, 2016
Messages
5,063
Likes
817
#8
What happens when you get beyond the speed where you can pedal effectively using that gear? Do you have to pull over, stop, get off the bike and manually move the chain up onto the next gear? Doesn't that make it difficult to get going again?
Nobody does that, you are one of the few that will care about the front derailleur on this site. Personally I left mine on the smallest cog for max torque for initial starting, the engine handles er'thang else! With a jackshaft you don't even get that option, you don't keep the chainring.
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,239
Likes
545
#9
Nobody does that, you are one of the few that will care about the front derailleur on this site. Personally I left mine on the smallest cog for max torque for initial starting, the engine handles er'thang else! With a jackshaft you don't even get that option, you don't keep the chainring.
Well, you don't; but the OP said he wants to keep the functionality of his mountain bike. He asked for some pointers on how to do this.

I would expect its more trouble to remove the existing front derailleur than it is to just leave the derailleur exactly where it is. A mountain bike needs something there to prevent dropping the chain.
 
Last edited:

gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
2,926
Likes
819
#10
The one problem I have found with front derailleurs is it gets in the way of mounting the engine. I'm sure this would vary form frame to frame. Once you jack shaft to a Nuvinci you'll never go back. Seamless shifting at full throttle. Run at a idle smoothly without jerking or dying, This is not a light bike but with a little tug on the bars and gassing it you can pull a respectable wheely. I finally grew a pair and tried it out, and it really puts a smile on your face. Effortless cruising at 35 mph. Worth every penny even though it was a lot of them. Oh and Jake I remember you saying you lost the plastic ring that goes between the grip and the shifter. I wound up making one from the plastic top of a spray paint can. Works perfect.View media item 61261View media item 61260
 
Top