Clutch questions

[Paden87]

I am going to put a gx390 in my doodlebug and I wanted to know what is the best clutch for it. I will be using the stock tire size which I think is 8" and I am looking for a decent speed around 45 or 50 at least more is better but still keep some low end power. I will also be building up the motor when funds become available.

 

[Poboy kartman]

I am going to put a gx390 in my doodlebug and I wanted to know what is the best clutch for it. I will be using the stock tire size which I think is 8" and I am looking for a decent speed around 45 or 50 at least more is better but still keep some low end power. I will also be building up the motor when funds become available.

Have you ever been on a Doodlebug at 50 mph?

 

[mckutzy]

I think a better question will be how is one going to stop on a DB( that should an occasion arise going down on a steep hill/mountain w/smooth road) going ~50mph..... ?

 

[FreeRunner15]

i can barely handle my bicycle at 20 mph downhill while "white-knuckling" and it has a longer wheelbase than a mini. Have fun with That one.
Just be careful on the turns. Good tires and knowing the road is key. small patch of dirt+speed+an angled wheel could mean disaster.

 

[chancer]

I dont know why everybody is harrassing you. Flyinghillbilly and Minibiker both have super fast minibikes. So hold out and you will get good advice from like minded nuts.

I do not see your CLUTCH QUESTION in your post?

 

[Paden87]

I have a 9 horse Briggs on there now. After I get off work I'll do a speed test to see where I'm at now

 

[anderkart]

I am going to put a gx390 in my doodlebug and I wanted to know what is the best clutch for it. I will be using the stock tire size which I think is 8" and I am looking for a decent speed around 45 or 50 at least more is better but still keep some low end power. I will also be building up the motor when funds become available.

Does your clutch need to be installed with its drive gear facing in-board (towards the engine), so your chain will line up with the wheel-sprocket ?

If your running a #35 pitch chain, I'd go with the Noram Star clutch. They're not cheap, but I doubt you'll find a better/more-versatile 1-bore clutch with as many cool features at any price.

I used this clutch model for years on my racekarts, let me know if you want more details

 

[Paden87]

I just got my noram star clutch in the mak along with some othe goodies and when I picked up the clutch box the clutch fell out and I'm not sure which way the clutch shoes go back or where the washer goes.

 

[anderkart]

That thrust washer goes in-between the drum and hub assembly.

The hub assembly will function the same installed in either orientation, although if one side of your hubs center section protrudes out further than the other side, test it each way and then select the orientation that centers the shoes in the drum.

 

[Paden87]

Sweet shank you so much

 

[Paden87]

I meant to say thank you. I really don't want to stab anyone unless I have to. But I have another question. When I put the clutch on it seems to sit far back on the crankshaft I have a excess amount poking out the front where the bolt would go. I wanted to know what I needed to do about it. Do I cut it off or shim it or leave it alone a just put a bolt and washer.

 

[Jrgunn5150]

Do you have it lined up with your sprocket there?

Either way, I would definitely shim it with washers before I cut anything.

 

[chancer]

Sweet shank you so much

Shank!

 

[anderkart]

Noram designed that clutch for the Tecumseh Star racing engine, they had a shorter output shaft that only protruded out a 1/4"past this clutch. This allowed the clutch to float 1/4" in & out to help keep the chain from being thrown off as the chassis flexes.

You could stack 1" ID thrush washers (on the inside or outside) of your clutch as needed to line up to your rear wheel sprocket. I'd leave a 1/4" float-gap and simply arrange the washers so the clutch perfectly centers itself between this gap as your spin the rear wheel with the chain on.

You know you can install this clutch with its drive gear facing your choice of inboard or outboard, right?
I'd think Inboard would work out best for a GX390 on a minibike

 

[Paden87]

Yea I know about the inboard and out board part and yes I will be running it inboard. Thank you for the info on the 1/4 inch part

 

[chancer]

But the 1/4" part was for Go Kart Frame flex. Will that apply or be necesary for a Mini bike?

 

[anderkart]

But the 1/4" part was for Go Kart Frame flex. Will that apply or be necesary for a Mini bike?

Doodlebug frames flex around like overcooked spaghetti. They have serious chain throwing issues with they're stock 97cc engines, and now were adding a much heavier engine producing way more torque...

---------- Post added at 07:12 AM ---------- Previous post was at 07:06 AM ----------

Yea I know about the inboard and out board part and yes I will be running it inboard. Thank you for the info on the 1/4 inch part

Your welcome

PS:
A very thin smear of Anti Seize compound on your output shaft, keyway and key will keep your floating clutch from galling everything up. Just a tiny bit goes a long-long way, don't want any slinging out onto the shoes & drum.