Please review my 196 clone build plan.

Mini Bike & Go-Kart Parts

MJL

Active Member
#1
Block/head -Hisun
PVL Flywheel
ARC Billet Rod (See below)
22 lb valve springs
Cam- Dyno Super X 265 lift
Head shave (See below)
3/4" crank
Bored stock carb (.650?)
93 octane ethanol free

I've got a Coleman 196 that my son broke the crank. Didn't seem to do any damage and actually still ran, so I'm planning on building it and dropping it in my Baja with a Juggernaut, 7 inch driver, and 10/70 sprockets. I don't do any cruising with the Baja, its all 50-200 yard sprints across our property, wheelies, and small jumps, so takeoff power/torque and throttle response are essential. I've got a Tillotson 212r in it now, which is great, but would like to see if I can do better.

Biggest question right now is the best way to increase compression. I'd like to aim for 10-10.5 (or should I go higher?). I can shave the head, or go for a longer rod, or a combo of both? I'd like to use the stock pushrods for economy reasons if possible. Will they still work with a .060 shave? I have not measure how far in the hole my piston is yet, nor have I called Dyno to see if the base circle on the Super X is the same as stock. Which brings me to my next question. Is the Super X appropriate for a low geared CVT minibike or should I be looking for a smaller cam (or even stock).

I do not like the way Mikunis stick out (likely to hit something where we ride) so I would like use a bored stock carb. Is .650 appropriate, or would .625 be better?

Last question, I would have a displacement and valve/flow disadvantage on the Tillotson, am I chasing my tail here?
 
#2
looks like a black mamba JR cam same lift and duration. I think with a torque converter and your limited breathing capacity it should work real good. As far as compression without knowing the in the hole measurement and the CC's of the head there is no way to know if it needs milling or if it does how much. I have more issues with a stock carb sticking out than a mikuni or flat slide. Pic #1 is a stock appearing carb on a fox mini. Pic 2 and 3 is a mikuni.
 

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MJL

Active Member
#3
looks like a black mamba JR cam same lift and duration. I think with a torque converter and your limited breathing capacity it should work real good. As far as compression without knowing the in the hole measurement and the CC's of the head there is no way to know if it needs milling or if it does how much. I have more issues with a stock carb sticking out than a mikuni or flat slide. Pic #1 is a stock appearing carb on a fox mini. Pic 2 and 3 is a mikuni.
Thanks. I can't measure in the hole until I get the crank in, but let's assume .020 for conversation purposes, and a 22cc head.

Your carb setup looks good, but most of the Mikunis are set up with a straight adapter on the Bajas because the angled ones put the carb and filter right in the mud splash zone.
 
#4
I see what your saying about the mud. I went out and looked on one of the compression ratio calculators. if you have a flat top piston then the folowing applies, if it is dished it wll be less. If you have a 22cc chamber, piston .020 ITH and use a .009 head gasket (which is ideal for a .020 ITH measurement) you would have a 8.9:1 ratio, if you have a 18cc head it would be 10.5:1 and a 15cc head 12.1:1. I think if you can get a ported stock type carb it would help you a lot. Any idea of the valve sizes?
 

MJL

Active Member
#5
I see what your saying about the mud. I went out and looked on one of the compression ratio calculators. if you have a flat top piston then the folowing applies, if it is dished it wll be less. If you have a 22cc chamber, piston .020 ITH and use a .009 head gasket (which is ideal for a .020 ITH measurement) you would have a 8.9:1 ratio, if you have a 18cc head it would be 10.5:1 and a 15cc head 12.1:1. I think if you can get a ported stock type carb it would help you a lot. Any idea of the valve sizes?
Pulled the head and checked the valves, 25mm intake and 24mm exhaust. Head is marked with 22. Everything appars to be direct GX200 clone. I found a shorter adapter that might work so I'm looking into the Mikuni, does it idle well without fouling the plug? That seems the be the biggest disadvantage of a bored carb for a mild build. As it is, I don't idle much and am sure to shut it down if I sit much longer than needed to put on gloves, etc.
 

MJL

Active Member
#10
Got my crank in today, installed it, and took my measurements. .030" in the hole. I figure if I go .020" over on the rod, and use the .010" gasket, I should have .020" piston to head clearance. Then shave .060" (which should still work with the stock push rods), should put me right at 10.6:1 per the charts.
 

MJL

Active Member
#11
Called Dyno, Base circle on the Super X is .868" vs .850" on a stock. Also thinking .020" piston to head might be too tight. Might drop back to .030".
 

MJL

Active Member
#13
Pulled the engine back apart today and polished the crank after seeing it was recommended for an ARC rod in another thread. Figured I might as well go ahead and do it. Got it back together and swapped out the Tillotson. Also swapped over my intake and open exhaust. Ran pretty well! Didn't have the snap off the line (or wheelies) like the Tillotson, but pulled very well through the torque curve. The throttle linkage might still need some work, as the funky coleman return spring is prone to bind.

Found a pretty convincing copy of the large body Mikuni on ebay, and a nice short billet adapter from EC Carburetors so I decided to give it a try. Also have the +010 rod, flywheel, and cam on the way. After much (excessive?) deliberation I ended up going with the CS cam. I just really love low end torque and didn't want to give up any more than I had to.
 
#14
Block/head -Hisun
PVL Flywheel
ARC Billet Rod (See below)
22 lb valve springs
Cam- Dyno Super X 265 lift
Head shave (See below)
3/4" crank
Bored stock carb (.650?)
93 octane ethanol free

I've got a Coleman 196 that my son broke the crank. Didn't seem to do any damage and actually still ran, so I'm planning on building it and dropping it in my Baja with a Juggernaut, 7 inch driver, and 10/70 sprockets. I don't do any cruising with the Baja, its all 50-200 yard sprints across our property, wheelies, and small jumps, so takeoff power/torque and throttle response are essential. I've got a Tillotson 212r in it now, which is great, but would like to see if I can do better.

Biggest question right now is the best way to increase compression. I'd like to aim for 10-10.5 (or should I go higher?). I can shave the head, or go for a longer rod, or a combo of both? I'd like to use the stock pushrods for economy reasons if possible. Will they still work with a .060 shave? I have not measure how far in the hole my piston is yet, nor have I called Dyno to see if the base circle on the Super X is the same as stock. Which brings me to my next question. Is the Super X appropriate for a low geared CVT minibike or should I be looking for a smaller cam (or even stock).

I do not like the way Mikunis stick out (likely to hit something where we ride) so I would like use a bored stock carb. Is .650 appropriate, or would .625 be better?

Last question, I would have a displacement and valve/flow disadvantage on the Tillotson, am I chasing my tail here?
I have the same motor with 22 pound springs, CS cam, PVL +4°key, ARC rod, 14cc gx160 head, non epa carb, 38/140 jets, billet intake and RLV. It honks. I need a better carb but without beating up the valves it really goes for an easy build!
 

MJL

Active Member
#15
I have the same motor with 22 pound springs, CS cam, PVL +4°key, ARC rod, 14cc gx160 head, non epa carb, 38/140 jets, billet intake and RLV. It honks. I need a better carb but without beating up the valves it really goes for an easy build!
Nice!

Does the CS cam have the same size base circle as stock? And, does the 14cc head use the stock pushrods?
 

MJL

Active Member
#16
Swapped my Huyai carb on the Hisun for the PK2B of my Tillotson to see if I could find something. Might have found a little power by the butt dyno, but had a hard time dialing it in perfectly. Maybe the pilot jet is a bit too big. Not too surprised. The PK2B is just supposted to be built to tight tolerances, not necesarily performance enhancing.

Got my PVL flywheel in, lapped it and mounted it with the 5 deg key I had on the stock flywheel. I think the 5 degrees in addition little bit of built in advance in the PVL was a bit too much. No kickback, but it was a bit harder to start and didn't seem to run as strong, so I reset it with a stock key. I filed around 2-3 degrees off of a key to try, but haven't put it in yet.

Wheelies are back! The lighter weight flywheel must spin up quite a bit easier than the stock one. I'd like to see aluminum flywheels promoted as a performance enhancer, not just a safety tax. Just the flywheel alone got the Hisun a lot closer to the Tillotson than it was before. Blipping the throttle and jumping little dips and humps is of my favorite things to do when I ride. Neither the Tillotson nor the Hisun will do it if you are going over 5-10 mph or so, but if you are crawling through some tight trails, blipping away is a blast!
 
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SAS289

Well-Known Member
#17
I thought the PVL's are just the stock 28 degree BTDC timing? Mine was. I used a 4 degree key to get it to 32 degrees BTDC. At about 2 pounds lighter than stock you are saving a small bit of engine power. Less work for the engine.

Is the engine already built or are you just playing with the stock engine?
 
#18
Nice!

Does the CS cam have the same size base circle as stock? And, does the 14cc head use the stock pushrods?
It's a 7,000rpm cam, aggressive ramping not a lot of duration. It's really easy on the valves as far as stock based performance cams. It only requires 18 pounds but I went 22 on the springs. The head is a 14cc gx160 aftermarket job ($45 or less) but it's the same quality and valves as the stock head so I figured why not! On a torque converter it punches hard but will rev out. Biggest advantage to this build is full control of the motors useable power. Best for trail riding where you want that power to punch you along and still run you 45ish mph up top depending on your gears. I've used mine on small tire and big tire bikes without a problem, it's a moderate build but very versatile and dependable. Not to bad on the wallet and super easy to do is just a bonus!
 

MJL

Active Member
#20
I thought the PVL's are just the stock 28 degree BTDC timing? Mine was. I used a 4 degree key to get it to 32 degrees BTDC. At about 2 pounds lighter than stock you are saving a small bit of engine power. Less work for the engine.

Is the engine already built or are you just playing with the stock engine?
I though stock timing was 24 degrees BTDC?

Anyhow, the PVL was just the first part to come in, otherwise it is still stock. The rest should be here this week. Instead of just doing everything at once, I want to make changes incrementally and see if I can tell the difference.
 

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