Dorothy, Heald VT-7 (anything goes) project ...

Mini Bike & Go-Kart Parts

Davis

Well-Known Member
#81
This is a great build seems all we get lately is predator builds and no flatheads this build is a breath of fresh air to me it's lookin sweet to me keep up the good work!
 
#82
Thanks amigo, I never know if anyone reads this build but I keep plugging away ... this is something I've been pondering ... not sure where its going but I'll keep posting, good or bad ...

Things I do like .. the Tecumseh H50 Racing motor ... also the Mikuni tho its got a learning curve to it.

Kevin
 
#83
I'm with Davis on this. I am interested in this. I learned Mikuni tuning a couple of years ago on a BS flattie, and once I got it dialed in, the throttle response was phenomenal. I never found much difference with the air bleed, but getting the clip set up correctly on the slide pin made huge differences that made simple jetting easy to dial in.

I suck on exhausts, because my tools are limited. I do know that Tecumseh's like as little back pressure as you can give them. I'd be thinking along the lines of a supported straight pipe, with possibly a quality muffler clamped on like RLV. You'll want to wait until the very last, so you can make sure you miss your seat support structure, and your body fitment to avoid those troublesome legfires. :)

LOL, best I just sit back and enjoy your efforts here though. Keen on watching it come together.
 
#85
Tiny Tach ...

Started the bike, the tach looked to be resetting itself .. and it did .. it went back to zero hours ... its working again ... I only really want to know RPMs so its good.

I bought the real McCoy and not a cheap knockoff .... hmmm ... luck of the draw ...
 
#86
I bet that has something to do with the motor having a non suppression plug wire. I had that problem with trying to run a bicycle spedo on a mini. they dont play well with electronics
 
#87
I bet that has something to do with the motor having a non suppression plug wire. I had that problem with trying to run a bicycle spedo on a mini. they dont play well with electronics
Hi amigo!
I get the impression this is what its designed for ... check their site out .... https://www.tinytach.com/gasoline-tinytach

As far as resetting itself it is not supposed to do that under any circumstances ... reviews are so-so, but its better than the Chinese ones. I just want the tach function anyway.
 
#89
Clutch issues ...

The Clutch will be replaced with a TAV.

Its hard to control this clutch in my application. I had to try it tho.
In a drag racing bike being able to feather it out and let it lock when you want it to would be the cats ass. It locks up hard, at least on my 9hp motor.

Problems I had otherwise ... (sprockets were aligned with care so that was not an issue)
The chain was chewing the sprockets (#35 & #40) badly.
#35 on top, #40 on the bottom.
My best assessment says master links should not be used, but I didn't see any thing on the 3D website about that.


First the #35 .... The regular links could have made those chew marks but the master link was definitely interfering.
Odd thing is the chew marks on the sprocket are every other link pin, not every pin like I would expect.
I measured the pin width and regular link pins were .520 while master link pins were .560

The #40 ... same issue as above but more pronounced as the chain is wider but the distance between the sprocket edge and the chewed area is about .210 on both the #35 & #40 sprockets. Add the wider master link and there is much interference.


When I moved from a 12 tooth jackshaft sprocket to a 24 tooth sprocket I ran into another problem, the chain was hitting the hex head that secures the guard to the motor.
This was causing the chain to get pushed twards the outside under load and popping the master link clip off and then the chain.



This might end up in my brothers hands as he is more likely than me to make a street racer ...

Kevin
 
#92
The exhaust is my next stumbling block ... I found some parts around the shop to fab this up ...
The spring is 1" O.D. and 1/2" I.D. ... it fits in the tube and is held with a cap screw. it's a continuous coil.
The flat ends of the spring have been cut off so
It can be cut as needed for sound/performance ...
It looks good on paper anyway ...
I hope to try it tomorrow ....
 

noseoil

Active Member
#93
Interested to see how this works. Can you post a couple of videos, one with the spring & one without? Looks like a good idea for a budget muffler build.
 
#94
Could you come up with a larger diameter spring? Say a 1 1/2 inch OD or even a 1 1/4?????

I am liking it so far.

I would think the longer the pipe the better sound control it would have to a degree.

Delray's pipe was pretty long.



Doug
 
#95
Ok, here's a video of the exhaust in action ...
[video=youtube;WPz4EBnKEiQ]https://www.youtube.com/watch?v=WPz4EBnKEiQ&feature=youtu.be[/video]

The results are more dramatic than the video shows .. the spring makes a big difference in sound.
Crank the volume on your speakers, its helps tell the difference .. yes really ... you hear the no-spring throaty sound.
And loud pipes mostly only save lives if they are aiming forward like horns.

This didn't do anything for the stuttering ... I will keep addressing that in the Mikuni thread.
https://www.oldminibikes.com/forum/engines-and-modifications/145083-tec-h50-oval-bore-mikuni-pics-videos-6.html#post1125849
 
Last edited:
#96
Ok, here's a video of the exhaust in action ...
The results are more dramatic than the video shows .. the spring makes a big difference in sound.
Crank the volume on your speakers, its helps tell the difference .. yes really ... you hear the no-spring throaty sound.
And loud pipes mostly only save lives if they are aiming forward like horns.

This didn't do anything for the stuttering ... I will keep addressing that in the Mikuni thread.
https://www.oldminibikes.com/forum/engines-and-modifications/145083-tec-h50-oval-bore-mikuni-pics-videos-6.html#post1125849
Me likey. I wonder what it would do with a length of pipe behind the spring? A tailpipe....

Doug
 
#97
For me a finished exhaust might have this spring near the end but held in place with a cap screw that wouldn't be so visible.

And yes I can get 1-1/4" and 1-1/2" springs ...

Me likey. I wonder what it would do with a length of pipe behind the spring? A tailpipe....

Doug
 
#99
Ok ... were back in this thread ... had some motor issues that I posted up in another thread ... you can read all 15 pages (so far) here ...
https://www.oldminibikes.com/forum/engines-and-modifications/145083-tec-h50-oval-bore-mikuni-pics-videos.html

I said I would be switching to a TAV ... I chose a Genuine Comet Magnum 44 series ... it came a few days ago ...


It came from OldMiniBikes, about $150 delivered.
I also ordered a 40 series genuine Comet Driven from BMI Karts, it will be here in a few days.
This was not on the OldMiniBikes site so I went elsewhere.

When the driven comes I can start work on the jackshaft ...
 

Top