Mikuni Y - N??

[Brian1A]

I have added a pipe and high compression head to my 66cc 2 stroke. Runs about the same BUT the big head fins realy keep it much cooler and it does not " gurgle " at certain RPM's any more.Naturally the next thing is a bigger carb. Being a motocross two stroke tuner I imediately thought to use a Mikuni VM 18 or 20 ( ?? ) However I do not seem to see anyone using a Mikuni carb. Thoughts-?? I am not trying to turn it into a racing eng. just looking to get a little more zip and of course... look cool

 

[Frankenstein]

I have added a pipe and high compression head to my 66cc 2 stroke. Runs about the same BUT the big head fins realy keep it much cooler and it does not " gurgle " at certain RPM's any more.Naturally the next thing is a bigger carb. Being a motocross two stroke tuner I imediately thought to use a Mikuni VM 18 or 20 ( ?? ) However I do not seem to see anyone using a Mikuni carb. Thoughts-?? I am not trying to turn it into a racing eng. just looking to get a little more zip and of course... look cool

That pull start won't do much other than piss you off in time. Wait untill it starts breaking every other pull..

Jaguar promotes the 18mm Mikuni, I think it's a sound decision as well.

 

[HumanPerson]

That speed demon muffler has almost 6 inches of header pipe/tube inside of the expansion chamber.
I've got pics showing where i cut one up and re routed it.
https://motoredbikes.com/threads/speed-demon-exhaust.49871/

Here you can see how i re routed it and added a few more inches to the header pipe/tube
https://motoredbikes.com/threads/new-build.49793/
Just cut it out then braze with some copper elbows and you'll be set to go

 

[Brian1A]

The Recoil starter- Your right a total Pile Of Sh.. Worked great for about 25 -30 pulls then locked up. So, I took it off and put t5he left pedal in position and use it like a kick start! Works great and now there is nothing in the way of my left pedal!! AS for the pipe, that pipe I have on there is an improvement but not a lot . So, I am building my own from scratch after getting my degree wheel out and opening up the ex port.

One other thing. I see a lot of people running " reed kits " but being a piston port engine to do it correctly you need to add boost ports. Does anyone currently have any specs on that mod?

 

[Frankenstein]

The Recoil starter- Your right a total Pile Of Sh.. Worked great for about 25 -30 pulls then locked up. So, I took it off and put t5he left pedal in position and use it like a kick start! Works great and now there is nothing in the way of my left pedal!! AS for the pipe, that pipe I have on there is an improvement but not a lot . So, I am building my own from scratch after getting my degree wheel out and opening up the ex port.

One other thing. I see a lot of people running " reed kits " but being a piston port engine to do it correctly you need to add boost ports. Does anyone currently have any specs on that mod?

I do the same with a jackshaft even though it isn't recommended, small push to get the wheel moving, then let the clutch out and give it a nice leg shove.

Works better with a warm motor, works ok to not at all in cold weather with starting fluid.

The boost port is definitely a good part of a reed valve mod, the same tool you could open the exhaust (not specifically necessary but helps) can make a boost port. Make it just a hair shorter than the transfers, 5 - 7mm wide and about 3mm deep, chamfer your edges.

You'll really really want to drill your piston skirt or cut a window in it for the reed to be of any use, otherwise it's still a port timed intake and the boost port would be a useless addition, if the skirt blocks the intake a pressured charge of fuel won't make it through to the boost port effectively.

Jaguar has a lot of info on that specifically in his website. This is the page on it, you'll see everything you could need to know on the reed valve and necessary modifications. http://www.dragonfly75.com/motorbike/reedvalve.html

 

[Brian1A]

So, I guess porting etc will have to wait!! I sold the bike to a college kid for $450.00 So, taking what I have learned from this I am going to build a better one!!