New Newb Big Time

[Crusade]

Hello!

I have been reading for weeks and cannot believe how much information and support is on this forum. I've had my fair share of hobbies over the years and have visited many many forums but have never come across such an up beat positive forum.

Pulled my fathers 75 cb750four out of the barn 6 months ago and started rebuilding it. It has been sitting for over 15 years. Got her going and suddenly had flashbacks to dumping it and getting some pretty good rash. Decided I should start small and work my back up!

Well this is where the motorized bicycle comes in. Made a silly silly uneducated craigslist purchase on impulse and boy am I ashamed. Knowing a thing or two about motorcycles and cars I felt comfortable in my purchase. Unfortunately I didn't know a darn thing about bicycles.

I have since then stripped the entire motorized bicycle and thrown away 75% of the death trap and have started fresh. I will say I rode said deathtrap just long enough to get the itch!

Quick question. Having difficulties with chain length on drive side (engine). It is too short. The only thing I can think of us the adapter I had to use for my large tube frame has my engine at a pitch that is not allowing for the desired slack?

Thanks

 

[xseler]

Howdy & welcome!!

If you get one of these tensioners from Turbobuick1, the chain slack won't really be an issue. Good luck with your build!

 

[2door]

Welcome to the forum, Crusade. We're glad you've joined us.

As for your chain issue; is this a new installation or are you simply re-doing what you have? Different bike? Different engine? 2 stroke or 4? We need a little more information about what you have.

If a new bike then the chain was probably sized for the original and you'll either need a new chain or to lengthen yours.

Tom

 

[Crusade]

Sheesh talk about a fast response.

2 Stroke, SD Stinger Motor. Purchased second hand but from a gentleman who did not seem skilled enough to change chain length. It is going from a mountain bike frame to a cruiser frame (cranbrook, yeah, I know).

Is anyway of knowing what my from factory length should be?

The position of where the motor is mounted does not seem likely eh?

 

[xseler]

My Skyhawk is in a 'Cranbrook' frame.....seems like I had to shorten the factory chain about 7 or 8 links, if I remember correctly.

 

[MotorBicycleRacing]

Kit chains are typically 5' or 60" long and 120 links.

Some HD bmx chains are only 98 links which is too short at 49" long.

415 41 410 chain are 1/2" pitch chain.

 

[maniac57]

You can easily adjust chain length by adding shims behind the rear motor mount block.
Just make the chain slightly long and shim till it's right. No tensioner required!
That said, I simply tack weld the tensioner to the frame stay for security on sale builds.
Much easier and still reliable.

 

[2door]

Original chain length isn't important, Chain tension after installation is. You'll want 1/2" to 3/4" slack. As I said above, if your chain is too short you'll need to replace it with a new chain or add links to make it longer. To add links you'll have to know exactly what chain you have. If it is the original kit supplied #415, you'll need #415 links.
My advice would be to replace the chain with an industrial quality #41 chain and shorten it to give you the recommended slack.
Are you using a chain tensioner? There are many Cranbrook builds here. Use the search feature, keyword 'Cranbrook' to see what others have done to motorize this particular bike.

Tom

 

[Crusade]

Alright then thank you very much for the advice. I'll take another look at now and see what I can figure out.

 

[MadMannArt]

I just bought some #41 roller chain from Napa.. bought a 10ft piece, comes with masterlink, I also picked up some half links...
Dude, if you can handle syncing the carbs on the Honda, you can handle this...
I had to stop over thinking it. Basically it is a ****ty chainsaw engine, it is that simple. I used a Manic Mechanic rear hub adapter on everything I build because I like them.. I"ve used the spring tensioner pictured above, they work great with a SMOOTH pully, mine kept jumping the teeth of the sprocket on it, I put the Roller bushing from the stock tensioner on it, problem solved...

 

[Crusade]

Just a quick update:

Went ahead and bought new chain based on all of the advice given here. Borrowed a chain breaker and away I went. Got the new chain on and did some adjusting. Lots of adjusting later on the rear end and I have a running bike!

I got insanely lucky though. Contacted a local member here on the forums about our legal status with bikes and it turns out he lives about a mile away from me!

We've hung out a few times and my motorized bicycle would not be running without him. Rat Bones is one **** of a guy.

 

[Tang]

welcome Crusade. Its the place where the party's at.

 

[paul]

that is awesome! welcome to the wonderful world of motorized bicycles!

 

[massdrive]

Welcome Crusade, Maybe you should call your bike "DeathTrap", to mock what it was and honor what it isn't anymore... Just a thought.

 

[Crusade]

I actually really like that idea for a name. Thanks for the suggestion Massdrive. The new build feels much more safe and the only thing left from the last motorized bicycle is the motor. But I do like the name. Thanks.

 

[massdrive]

I'm an old school gearhead and for better or worse I truly believe that every machine has its own personality.