VIDEO modified '79 Kitty

[t-dub13]

Hey Guys, I've finally gotten some video of my Kitty running pretty well.
See a couple laps in the driveway here: http://s13.beta.photobucket.com/user/be ... 2.mp4.html
Mods include:
Dantheman's lift kit with added ski spreaders
Re-chambered head 12:1 compression
Ported for 5500 RPM
Mikuni VM20 carb from a 1980 Yamaha YZ50
Mikuni fuel pump
Drilled clutch shoes and stiffer spring
13T clutch outer
Mountain bike handlebars

This thing is so much fun! I'd love to race a 120 on it. haha

Next mod will be either installing a GY6 clutch and belt from a scooter and adding a jackshaft OR building a tuned pipe, whichever comes first.

[72]

Looks like fun, any plans on pulling a back flip off that hill?

How was getting that carb dialed in?

[t-dub13]

I used a Tecumseh carb spacer from an old Ariens 6hp snowblower to mount the carb. Looks like this:
I used long bolts through the carb, through the spacer and into the cylinder flange. It bolted up nicely with just a slight bit of grinding. I also tapped 1/8" NPT hole in the spacer and took the pulse from there to run the fuel pump. Youo can sorta see it in this pic:

Initial jetting was off, but it ran OK. I'm now running a 160 main, needle in the #2 position from bottom, and a #20 pilot. Plug is light brown. I'll go with a 162 main since testing was done at 36* and it's going to get colder soon. Had no detonation or heat problems yet though. But I am worried about the tiny exhaust pipe restricting flow and holding the heat on the piston crown. Another reason to go richer.

Oh, FWIW: The Winderosa gaskets are excellent quality, but the head gasket is .010" instead of the stock .020". It will raise the compression a bit in the stock engine, but I calculated my squish and compression assuming .020" head gasket, so I haven't used the Winderosa gasket yet.

[t-dub13]

I'm glad we can now post pics here! Here's a pic of the clutch shoes and how I drilled them. 1/8" drill through and then a 7/16" drill spotted on the back side.

And a pic of the sled with the mountain bike handlebars.

Side view showing the original Dantheman's lift modified for 2 inch lift (I think) and then modified again for 3+" lift haha. And the ski spreaders added on.


I got the clutch outer from JONN at OBUPS and I'd highly recommend getting a stronger spring from him too!

Here's my first time hitting the snowbank.
http://s13.photobucket.com/albums/a274/ ... cc6ea8.mp4

[929rog]

wow that thing sounds good. I had a 18mm on mine back in the day and really helped it but nothing like that. I got a 50cc pocket bike pipe I was going to use years ago and never got around to it. Would not be much trouble to make it fit I think. I'd sell it to you super cheap.

[t-dub13]

Thanks Rog. CHECK YOUR PM's!!!
I already have a bunch of MX pipes for 60's and 80's though. Problem is that they're tuned for 10-11k RPM and I need a pipe tuned for 5-6k RPM. The MX pipes are about 1/2 as long as they should be for this motor / application. I'm going to build my own custom pipe for it when I get the time. What is the top RPM of the pocket bike that the pipe is for? I might snag it anyway. Thanks!

edit: Looks like stock pocketbikes turn 6K and modified ones can rev up to 12K. Might still be easier to modify a pocketbike pipe...

[929rog]

It's a stock pocket bike pipe. The only thing I was thinking was might need to make the stinger a little bigger. Almost forgot this one ... I remember guys taking the stock pipe and cutting the "downspout or stinger" off then using a larger tube in place for better performance. Just can't remember the size. I did one years ago and I think it was 3/4 but same length. It helped wake it up. Stock pipe is so restrictive.

[t-dub13]

Yeah, anything would be better than the stock pipe. I have a pipe designed for it, but no time to build another pipe. Retrofitting a pocketbike pipe would probably help quite a bit. Can you post a pic?

I was thinking about purchasing this one... for like $60 something.

Plenty of curves to play with. Cut, turn and weld... I would also have the end of the stinger exit into a larger muffler to keep noise down. I think I could find th eroom inside the cowl.

[72]

For the pipe to come in at 5500-6000 rpm it would have to be around 36-38 inches long from the exhaust flange not including the stinger. Thats going to take some creativity.

[t-dub13]

Both my pipe programs come up with 50"-54" depending on the BMEP, HP and how wide I want the powerband. Yes, it's certainly going to take some creativity!!! I think it will look pretty cool with a pipe snaking around in front of the motor.

72: How did you come up with your total length???

EDIT: mine was total length... without port and stinger length, I get 36"-38" also. Thanks for the sanity check.

[72]

Keep in mind that pocketbike pipe with all the curves are two stamped halves and very thin, the cross section is not even close to being round, this could provide a very difficult situation for the cutting and turning you plan on doing, just a heads up. A quick down and dirty exhaust mod for the stock exhaust is to cut off the stinger and drill a hole as large as you can in the baffle (through the hole left by the stinger) , or two if you can angle your drill enough, then weld on a larger diameter stinger. 1/2'' emt will work. This will definitely help with flow and heat and really doesn't take much time. Of course with the increased flow, so you most likely will have to jet up a little. I always wanted to try to route a pipe through the upper part of the tunnel with a lift( seat warmer), it would look cool exiting out the back but I suspect the location would change temp too much.

Quick question, did you just stuff a goose neck down the steering post to mount those bars?

[t-dub13]

Thanks for the tip on modifying the stock pipe. I didn't see it when rog explained it. I might pick up another stocker on ebay or somewhere to modify, but I think I want to save a stocker too. Not making enemies out of the neighbors is pretty important to me.

I'm a little concerned about the performance pocketbike pipe and it's ovality and paper thin walls. ...Haven't decided on that one yet. Rog has a stock pocketbike pipe I want to try modifying first.

RE: The mountainbike handlebars. the gooseneck ID was almost large enough to fit OVER the steering stem on the kitty. I did some cleanup of the steering stem and opened up the gooseneck (cut a slot up the side) and it eventually fit. There was probably .015-.020 difference. Once fitted, I cross drilled two holes and used 1/4-20 shoulder bolts, grade 5, with nylock nuts.

[brad dodge]

CALL OLSON HE COULD HOOK YOU UP WITH A CUSTOM PIPE $$ will be right MB

[t-dub13]

I got antsy with the blizzard of 2013 hitting here in the northeast and decided to modify my YZ60 pipe to fit. I used part of an XR400 header pipe to extend the head pipe, and used an XR350 header pipe to make the silencer / tailpipe. I used two Arvin Briggs and Stratton canister mufflers for silencers. I may stuff them with coarse steel wool if it's too echoey. I snipped the heads and points off of some finishing nails and bent them to make spring loops. My welding helmet is trashed, so couldn't see to well while welding these. Someday I'll get a new helmet and make welds that arent embarrassing!

The added header pipe and belly section brings the length to the target 38", so hopefully this performs well.

The blizzard hit and I had to tend to everything else, and so-far I've only started it and idled it for a minute. It idled waaaay high, so I turned the idle down and it sounds awesome. Can't wait for some time to take it out.





I will report on the performance as soon as I get a run!

[t-dub13]

I got on it and gassed it. It hung the skis for 15', scared the tar outta me! Amazing low and mid range power. Fell flat on top, so I've got some jetting to do. If it's still flat on top with good jetting, I'll cut an inch out of the header pipe, then maybe open up the transfers some more. I think I'll stay with 119.5* duration though until I get the rest sorted out.

This machine really needs a CVT though. I'm looking at the Tork-a-verter type and also the CVT's that are on GY6 scooters. That's a project for next fall though.

[72]

Nice, whats your peak rpm?.........Vids?

[t-dub13]

No tach, so I can just guess that it's got great power up to about 5-6000, then it's running out of main jet or the header is too long. I ported and piped it for 5-6000 but was hoping for some overrev for short bursts.

[72]

No tach, so I can just guess that it's got great power up to about 5-6000, then it's running out of main jet or the header is too long. I ported and piped it for 5-6000 but was hoping for some overrev for short bursts.

Thats a tough call without a tach. With that rpm range there is a finer line, does it seem to get even a little better if you keep the throttle held down..... or does it just spit?

You could throw a cell phone in your pocket that has a gps speedo calculater on it, the next time you open it up. Working backwards from there might give you a hint of where your next move should be or aimed at..... good luck ... still waiting for the vids

[t-dub13]

I can't even get enough snow here to test. It's been so slushy and mushy here. Yesterday was rain all day and 40 degrees. UGH!

Last time I rode it, I could get some overrev, but I had to feather the throttle like it was starving for fuel. If I whacked it WFO it would almost stumble and fall off a bit. Just wouldn't make any more power. I haven't gone up on the main yet.

Now it's too muddy to even do a grass drag launch for video.