MB165s DB30 open class entry

Mini Bike & Go-Kart Parts

MB165

Active Member
#21
OK, I just ordered up a clutch, chain, 12t and 15t sprockets for the jaskchaft.
My plan is to mock it up as complete as I can before I drill anything. Im going to get a long 5/8 bolt from the hardware store for a temp. jackshaft. I have no idea how long the finished shaft needs to be.
I finally get to use my degree wheel I bought from Peekster at windber for setting the timing. Anybody know a good starting point?
 
#22
OK, I just ordered up a clutch, chain, 12t and 15t sprockets for the jaskchaft.
My plan is to mock it up as complete as I can before I drill anything. Im going to get a long 5/8 bolt from the hardware store for a temp. jackshaft. I have no idea how long the finished shaft needs to be.
I finally get to use my degree wheel I bought from Peekster at windber for setting the timing. Anybody know a good starting point?
Depending on how things lay out mine is 10 inches long.
Buy the best steel!
I am tearing up belts, eating bushing and on my last inspection my keyways are showing wear of the high shock loads.
Its not because things are loose.
I have that shaft gooned up to 50 foot pounds.
 

MB165

Active Member
#23
switching over to some engine work till the sprockets come in...


I hooked up a degree wheel and a piston stop and located TDC. The cam card says 30-32degrees timing advance, Its set to 28 degrees, 5 more than stock, im not sure what to expect so I figured less is better to start out with.


magneto air gap is set to forty thousandths. Its a Stens brand but it says its made in Germany.
.

I won the robertson torque tube for $15 on ebay...


Walbro PZ 22 carburetor, also from ebay..$22. I had to heat and bend the choke lever up, it wouldnt clear the exhaust. Manifold is a E.C.bert item.
Anyone know what the pipe fitting is for?


Thats all for now.
 
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MB165

Active Member
#30
more progress....
I got a 5/8 bolt on order from BMI for the jackshaft, its got the keyway cut, it'll need maybe an inch trimmed off it and that should take care of the drive setup. Still need to get a pitbike throttle and cable to fit the PZ22, and a small valve head from ARC.

Been working on the fuel tank some, relocated the front mounts and got it pretty much ready to mount.


I had some left over silver solder, thats what i used to attach the new mount to the tank.

busted out the gasket cutter and used some plumbers rubber gasket for isolators.



the bracket was welded on crooked by the factory, I just went ahead and made big holes once i found out the small ones i drilled wouldnt line up.:shrug::laugh:

Theres about 1/4" of clearance.

the petcock is even closer! less than 1/8", I had to grind on that area just a little.

 

MB165

Active Member
#34
Another piece of work by ARC racing.....


This was designed for the engine builder, as there is lots of extra to mill if needed. Clearance-wise I could mill 1/8" off, and still clear the valves. For now its going on as-is. I hope it isnt hard to start.



.027" copper head gasket coated with some copper spray to fill any micro voids.


Finished up brazing the braces on the pipe....


 

MB165

Active Member
#39
done a little more on the DB.
Fuel tank is painted with rust olem yellow, I also switched petcocks. The one supplied with the tank is grossly undersized for minibike applications. I got a 1/8" npt vavle from ombw. Surprisingly, the threads in the tank only need chased with a pipe tap and the valve screws right in. Its a close fit, over the winter Ill pull it apart and trim some off to clear the frame. fuel hose is tygon with a fiberglass sleeve from Mcmaster carr.




Pitbike throttle off ebay with a honda CR500 cable


I played with gearing and came up with two ratios, road ratio=6:1 should be good for the Windber parade, and off road ratio=7.1, should be good for riding around Jeffs place.


Im building a slotted tensioner which will attach to the new crossmember, it should allow for some quick gearing changes.



seat is off ebay, custom yellow was done at no extra cost.
Engine RUNs....and its fast. Sounds good and its very loud with the straight pipe. Idle is higher and a little choppy compared to a stock engine. low end/ take off is somewhat mild, but definatley more power than stock. Mid range power comes in like a two stroke, it hits hard and pulls hard to what seems like 6500rpm.
Starting it is a bitch, gotta pull off TDC or it'll rip the handle right out of my hand. I got a good start proceedure down and with a leather glove it starts on first or second pull.

 

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