Custom Frame For Thumper Motor

[Lurker]

I just stumbled across this post, and I can't tell you how excited I am to see other people really stepping up their builds with a more reliable power plant with so much potential. I feel like this is a turning point in motorized bike building. It's only a matter of time before some one figures out how to make a "kit" with larger and more reliable engines. Keep up the good work and I can't wait to see the outcome of this build.

 

[oldtimer54]

I just picked up one of these motors for $59.98 + tax for a total cost of around $65.00 and I cant wait to get started. So what are you going to do for a clutch or are you going with a tranny?

 

[matthurd]

I just picked up one of these motors for $59.98 + tax for a total cost of around $65.00 and I cant wait to get started. So what are you going to do for a clutch or are you going with a tranny?

got a link or was it in a store?

 

[oldtimer54]

From HF for $74.95 less 20% off coupon. That coupon ended today but I have a new one for you that is still for 20% off any one item: 20COUP

 

[sketchman]

This is AWESOME!

 

[bonedeath]

Just curious what kind of welding/tubing you're using for this frame. Fellow welder here. I've welded up some bicycle frames before, and have a few ideas for the same motor.

 

[culvercityclassic]

Worked on the bike today. Made the motor mount, custom brake arm for more tire clearance, the bottom bracket with gussets, mocked up the carburetor setup and made some tabs for the tank.

Venice Motor Bikes hooked me up with a CUSTOM set of Worksman Alloy Wheels with a front disk hub…these rims are the SH-T…

I am waiting for the transmission so I can mount the motor.

Hey Bonedeath:The tubing is mild steel .065 and using a mig and tig.

 

[Venice Motor Bikes]

I know I'm gonna regret letting go of those wheels!, but i know they're going on a really nice bike!

 

[bairdco]

that's a cool Play-doh Pumper sprocket!

 

[NEAT TIMES]

As `arty` from "laugh in" would say; very interesting!! Will be a great ride for sure. Thanks for sharing!

Ron

 

[culvercityclassic]

I received the CVT that I ordered from AGK and must say it is a VERY well made part. I have been so impressed with the quality of the parts and support from AGK that I may never venture back to the china doll engine kits again. The quality you get and to see a label on a box that says MADE IN AMERICA is what it’s about.

I also have a torque cam, valve springs and a billet rod to install. I still have to order the fuel pump and flywheel. You think a Morini is expensive…try this build…

This is the latest mock up for the engine mounting plate. This motor is also going to get other supports on the top end of the motor. I have been delayed due to a broken tig welder, it stinks because I owe someone a tank and have not been able to fulfill my commitment to them.

I was trying to not have to order wide cranks for this bike but it looks like that’s the only thing that will work. I will be bull-legged after riding this punk. O-well

 

[scotto-]

Oh am I liking this build....this baby is coming together beautifully, look out!!! Man, 10+hp w/cvt, this is gonna be untouchable.....SERIOUSLY! You are breaking some serious boundries Jeff and doing a great job of it.....mind if I take it for a spin?

I truly can't wait to see this build finished, I'm sure you're as excited as I am 4-strokes gonna rule, yes they are!

 

[Goat Herder]

I have been eagerly watching! I is jealous

I have been fascinated with this motor and the CVT concept. This thing should be Awesome!

 

[culvercityclassic]

Mounted the motor. Changed the head tube and angle. Test fired the motor. This thing is a beast, shoots fire out the exhaust....

 

[Venice Motor Bikes]

That things looking pretty sweet!!!
Do you think you can get in done in time for the Willow race?
I'm trying to get the Felt Slater ready just to run some laps on the big track!!)

 

[tomgndallas]

Really awesome!!

 

[agk]

That brace you made coming off the cylinder head looks like it will do a good job supporting the engine. The header you made looks really nice too. It's going to be loud!

I would suggest using the stock plastic fan on that non-finned REV flywheel. The non-finned flywheels work great for a few 1/8th mile or 1/4 mile blasts. I don't have any experience using a non-finned flywheel for several laps on a road course in 90 degree weather. I would at least use the fan while you get the carb jetting dialed in and determine the proper oil level for this arrangement. Then you could get a baseline engine temp with the fan before running the motor without. I realize the race is right around the corner and you will not have much time for experimenting with and without the fan.

My go kart motor will get hot on warm days running on our dirt oval track. I have the fan, cooling tins and blower housing in place. When the cylinder head temp reaches about 440 degrees I will let off the throttle and cruise around the track for a few laps while the engine cools down. It seems all the cooling parts do their job at lower speeds and the air passing over the fins on the cylinder head at high speed is not sufficient to cool the motor.

My go kart motor is a 6.5hp Harbor Freight engine. It may not, however, be a good comparison as my motor uses high compression and some other mods that may contribute to running hot on warm days at the track. I just want to share my experience with you as it may help you with your engine mods.

 

[ocscully]

Perhaps a silly question? Where is the output from the CVT?

ocscully

 

[NEAT TIMES]

Ocs

The rear drive sprocket should be between the main mount plate and the driven sheave. It may have option of being changed to a pulley for rear belt drive also.

Ron

 

[Bigboy]

Nice!
Would be great to see your bike in Willow Springs!
There will be a lot to see!!

Roland & Timm
Bigboycycles