Getting more power, high compression 66cc...

[keatonx]

I finally got my Mikuni Vm18 carb and jaguar CDI 2.0!

The Cdi seems to work really well, I did not notice any power increase but my 66cc does run smoother so that is a plus!

Here are the mods I am working with setting up the new mikuni:

High comp. Fred Head 5.3. 145psi
44t sprocket on 29 in tires
Jaguar Cdi 2.0. With NGK plug
High air filter
Stock exhaust with mild drilled baffle
Custom gaskets, matched intake and exhaust ports.

Setting up the Mikuni for first run:

I had to make a custom intake to branch off of my 18mm port intake. 1. To fit the 22mm clamp style fitting on mikuni and 2. To mount the carb not to hit the frame.

The first air filter I tried greatly restricted the air flow so I adapted a bigger performance one to carb.

I used some thick plastic tubing I had laying around the house to make an offset intake with 22mm end. I used JB weld and hot glue to hold the press fittings together with a clamp on stock intake.
Here are some pics:
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I was able to start the bike and adjust the air and idle. With the number #70 main jet it and needle on lean setting it sounds awesome revving up with clutch in. When hitting road however it still runs rich at top end reducing my speed greatly, it got better the leaner and leaner I set the need and screw adjustments. But still could not get lean enough at top end sounded like 4 cycling. Not bad at idle or mid range though. So I believe I need a smaller main jet, I have a #60 and #65 on the way! That will be the next test!

I also am in process of making a more permanent, metal, slighter offset intake manifold.

I will post an update when I get her dialed in and show the progress.....

Gas will dissolve hot glue into a sticky mess very fast, I used it to hold my ram intake onto the carb of my 2 stroke lawnmower bike. The glue turned to mush from the gas from the carb

 

[MAFirst4]

Gas will dissolve hot glue into a sticky mess very fast, I used it to hold my ram intake onto the carb of my 2 stroke lawnmower bike. The glue turned to mush from the gas from the carb

Wow I had no idea that is good to know, thanks. I'll keep an eye on that intake. I used jb weld on too of the glue so that should hold it. However I wonder if that glue after dissolving gets sucked into the engine. That can't be good.... Iv only put a few miles on her I better check that now. Thanks for heads up.

 

[MAFirst4]

 

[66ccCruiser]

Raise the needle on your carb your too rich, drop the clip a notch...

Hey all,


I have been modifying my 66cc 29inch cruiser this past month and I have just a few questions. Here's where I'm at, I run the speed carb with the clip on the needle second from top. I have a mild expansion chamber exhaust pipe and the Fred high compression head installed. I am running a champion cj8 plug.


She runs pretty well overall, I'm 220pounds and it does about 27mph on flat over 30 downhill but I feel like it can do much better. I notice after about 20mph it goes from 2cycling to 4cycling. It continues to pick up speed but seems to bog as it does, or not sound like a real 2cycle should.


Why is it 4 cycling? It's not rich the plug looks great. Do I need to get a better carb? And what carb can I get that is the most adjustable? What about Cdi. I know there are some out there like jaguar, but will they help run my high compression engine and stop 4 cycling, do I need more spark? Different plug?


any information is helpful. And anyone running the 5.3 original Fred head, let me know your setup with it!!!
thank you!


-BrettView attachment 51727View attachment 51728

I mean Lower the needle a notch to run a little more lean on the top end!!

 

[66ccCruiser]

Pipe makes a difference...

Then there is this bad boy:

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I have this pipe from arrow and it gives the engine a motorcycle type attitude with a range of power with port matching done and a thatsdax perf slanthead and 36 tooth sprocket here in Sacramento with decent acceleration and 35 plus mph cruise and more if I want to ring it out to high vibration levels...Also have the jaguar ignition with the cdi box in the leather bag on the bars with rt carb and a boost bottle that actually helps my lower end torque with take off...these are prior pics of the ride a couple of months ago when the 41 tooth sprocket was on my steed... I try to show restraint and not tear it up too much to keep a good rep in my area...it's too easy to get cruisin in a hurry...

 

[Deleted member 12676]

4 stroking means it's too rich which means you have to lower the needle by raising the clip.
The CDI has to match the engine. A high compression engine needs less high rpm timing advance which the Jaguar CDI provides.
Put a good carburetor on it. Look at what I suggest on my site.
Most of the high compression heads give too much compression. This causes the chrome to flake off of the cylinder lining. Get a compression tester to check what your engine has. Anything over 135psi means you need to dremel away at the inner dome of the head to make more space there. If you cheat and add another head gasket then you ruin the squish area which then makes that part of the head ineffective.

 

[butre]

That's never been my style. I have only two throttle positions: idle and full throttle; done faster than the blink of an eye.

I've got a 19mm carb on my 66cc, I do the same idle and wide open thing you do and don't have any problems

 

[66ccCruiser]

4 stroking means it's too rich which means you have to lower the needle by raising the clip.
The CDI has to match the engine. A high compression engine needs less high rpm timing advance which the Jaguar CDI provides.
Put a good carburetor on it. Look at what I suggest on my site.
Most of the high compression heads give too much compression. This causes the chrome to flake off of the cylinder lining. Get a compression tester to check what your engine has. Anything over 135psi means you need to dremel away at the inner dome of the head to make more space there. If you cheat and add another head gasket then you ruin the squish area which then makes that part of the head ineffective.

I don't know what I was thinking yea thats what I meant...lower the needle by raising the clip...

 

[HeadSmess]

Anything over 135psi means you need to dremel away at the inner dome of the head to make more space there. If you cheat and add another head gasket then you ruin the squish area which then makes that part of the head ineffective.

just make sure, while you do this, and worry about "ruining the squish area" that you take the time to remachine the top of the cylinder to remove that dirty big chamfer that already HAS ruined the "squish area", and then remachine the head to clear the piston crown, because thats how much material needs to be removed to get rid of that chamfer.


of course, dont take my word for it. but it would be nice to read up on it on, oh...about page 47 i believe... whole chapter explaining it, and why that chamfer defeats the purpose of even thinking about squish bands on THESE engines

http://www.amrca.com/tech/tuners.pdf

(dont stop at just reading one chapter, mind you )


and also, make sure you ramp your piston at the same time, just to make sure any chance of having a squish band is completely negated though we ALL know that ramping the piston is a permanent fix rather than just testing modified port timings before destroying a (often expensive) cylinder