78 liquid fire. Wants to go Faster???

[Countryfuntime]

Hi. New to the site.

Looking to make my 78 liquid fire quicker?
Wondering if you can double gasket the cylinders?
Cut the head to compensate? What would be a good squish?
Would any other Reed cages fit. in this motor?
Any clutching suggestions? Ramp? Spring?



Appreciate any input

Thanks

[JDT]

So just how fast is it now?

340 or 440?

[harleysportster]

Before any engine work or clutch work, inspect the suspension and steering. The old sleds with worn out parts are not safe at fast speeds.

[Countryfuntime]

It is a 440. Looking for someone that has already did mods
To the motor to step up On Performance. do a lot of vintage rides with a bunch of friends
With this group you got a hold your own"yes in the works a rubber track is on its way'thanks

[WinnipegStPaul9]

Countryfuntime if you want to go faster I would suggest a different sled. Not trying to be funny, just honest.

DA

[JDT]

Vintage rides by definition are not races or places to show off your modifications.
The fact that you have made the machine reliable and run decent and safe are where heads will turn at Vintage events.
Many owners take pride in keeping there sleds stock as built original examples.

If you are looking to mod a sled for racing that is another story.
Building a sled up for drag racing, oval racing or cross counrty racing are all very different avenues.

A stock 440 78 L-fire will stand on it's own against many other machines of that era.
So my advice is to first rebuild the entire machine stock than reevalute your needs vs what it was like new.
You may be pleasently suprised with your efforts.

[Kurts]

It's unfortunate that so many people discourage others from tinkering. That being said, it seems as if your looking for someone to give you instructions on how to go fast. That's not going to happen.

I suggest you find a copy of "The Two Stroke Tuners Handbook" and read it cover to cover. Then go from there.

However If I were looking to just go fast on a vintage sled my choices in order would be
1. 81 El Tigre 5000, I had modded one, and it was the baddest vintage sled around. From 0-70 nothing would touch it. And the parts availability is good.
2. Arctic cat El tigre 6000, either 440 or 500cc
3. SRX
4. Early liquifier, The late engine are junk for making power.

[That Girl Racing]

What makes the Kawasaki liquids junk for making power?

[Kurts]

Look at any modern 2 stroke. Reeds and lots of transfer port area. Kioritz is right there, also has a small bore long stroke, easier to scavenge these motors without retarded amounts of duration.

Look at a kaw, piston port and no port area. Sure a piston port motor can make more peak power, but it turns em in to turds elsewhere.

No boost ports on the kaw, that's bad for scavenging too.

[That Girl Racing]

There you go! Learn something new everyday.

[Countryfuntime]

Gentlemen! Thanks for some of the good news and bad news.
No I'm not making this into a race sled
Yes it's all about having fun with these Vintage Sleds very knowledgeable on Skidoo'
This year I will be taking this liquid fire and yes tweaking is a must. we have a huge group from one town goes to Harbor Springs Michigan. For their annual vintage ride. there'll be a Srx GPX TXL's Rupp nitros and a few blizzards. Just asking some experience John Deere guy that's already tried an true. Some bolt on mods different ramps? Springs, something that will give the JD a little bit more if I can add 2 to 3 Sled links from stock that would be perfect. And yes there is a spot where people will lineup just to see your accomplishments'

[Kurts]

Granted that is just my opinion, but I'd say it's pretty grounded based on the progression of engine technology Look on ebay at some pictures of different cylinders The fast stuff is always lots of transfer area, and either reeds or rotary valve like the skidoos.

Piston port induction is not the best because you have symmetric port timing, that means when you get enough duration to make big rpm power, the intake port is open during at least half of the transfer cycle. So it just blows about half the charge back out of the crank case. At high rpm it's not a problem because the pipe helps suck it thru, also the incoming charge has enough momentum to defeat the piston trying to blow it back out. This all falls off (looses effectiveness) to basically 0 at 0rpm.

The book I listed talks about all off this, and you don't need to be a math whizz to understand it. I encourage everyone to read it. I have a digital copy.....

[Kurts]

Gentlemen! Thanks for some of the good news and bad news.
No I'm not making this into a race sled
Yes it's all about having fun with these Vintage Sleds very knowledgeable on Skidoo'
This year I will be taking this liquid fire and yes tweaking is a must. we have a huge group from one town goes to Harbor Springs Michigan. For their annual vintage ride. there'll be a Srx GPX TXL's Rupp nitros and a few blizzards. Just asking some experience John Deere guy that's already tried an true. Some bolt on mods different ramps? Springs, something that will give the JD a little bit more if I can add 2 to 3 Sled links from stock that would be perfect. And yes there is a spot where people will lineup just to see your accomplishments'

This is tough, really what I'd do is find another good cylinder, and do a complete time area study, per the book I referenced. Then I'd consider having a base gasket shim made, maybe like .060" Then lower the port floors to meet the pistons. Also deck the block to get the quench back. You'll need to shorten the fat section of pipe just a bit. This will push the power peak up in rpm a bit, so you'll need to clutch on it. Would be pretty unnoticeable.

Basically you have 2 choices
1.) learn and tinker
2.) send the engine to a 2 stroke builder and have them do the porting and the pipes.

[harleysportster]

Simplist thing would be to syncronise the carbs with a flow meter. No other method compares. If you want a little more off the line, install 340 chaincase gears and raise the idler closer to clutch engagement.

[Countryfuntime]

Thanks gentlemen for your input. I will put the info to good used. Thanks again"