440 Liquid Cooled motors comparison

[Macs80hp440]

I've always appreciated the classic look and character of the vintage sleds.  After about 15 sled transactions (buy&sell) in 3 years I might consider myself a sled nut.  However, am realizing one thing different between the Invaders and all other liquid cooled 440's of the day.  Invaders do not have any reed valve and still obtain 70+hp.  By comparison, all the other high performance LC motors had reed valves (or rotary):  SkiDoo Blizzard, Rupp Nitro, Arctic Cat elTigre, Yamaha SRX, Polaris Centurion...  Hec, even the larger 500cc motors of the day had reed valves, and the Interceptor did not. 

Also, all these other motors had dual pipes.

The Point:  All these stock "trail sleds" 440 L/C motors obtained low to mid 70 horsepower with reed valve AND dual pipes.  Kawasaki got the same without reed valve and one pipe.  So- I am wondering how much more overall power does a reed valve and 2nd pipe create, and can a reed valve assembly be retro fitted to the Invader...?

I know their are many other modifications and combinations.  I'm just wondering about the reed valve portion of it.

I guess I'm impressed with what Kawasaki obtained by comparison and wonder why they did not use reed valve and 2nd pipe (in the Invader).

Anybody else ever wonder about this?  Or am I the only observant geek in the bunch...?

[gixxer6]

Other than the Ski Doo having a rotary valve, I'm not sure about the other sleds that you listed, but the 79' SRX's and the Centurion didn't have reed valves.  They were piston port motor like the Invader was.  And the Centurion had a single pipe. 

IMO, the Invader engine wasn't anything super special, it was on par with the other manufactures of the day.  It was a two person sled, and it was tuned to be trail friendly.  Opposed to the high reving lake racer characteristics of the twin piped SRX's. 

[Macs80hp440]

Yes- and I actually mis-spoke about the pipes on the Arctic Cat elTigre, it was a single pipe also.  Yes- Invader is primarily a family trail sled and other comparisons are suited more for high speed single seaters. 

At any rate, in some research and conversations I've heard of other motors being fitted with reed valves.  Is this possible to put a reed valve assembly on a piston port motor?  Has anyone tried on the Invader?  I'm just looking for an idea to play with as I rebuild my Invader.

[Shawn]

By the time the Invader went into production the economic climate in America along with the emergence of OPEC placed a lot of pressure on snowmobile manufacturers. Keeping production costs low was a serious concern. The piston port design having fewer moving parts cost less to produce than reed/rotary valve designs. A single pipe giving comparable performance to duals offers a 50% cost savings. The piston port design offers simplicity. The single pipe further offered a near 50% weight reduction. These facts were certainly considered by Kawasaki engineers and production managers. Kawasaki engines were of their own proprietary design and manufacture. This wasn't the case with Ski Doo and Rotax or Polaris and the various engines they contracted to use. Though they participated in racing Kawasaki didn't really produce any models intended specifically for racing. Yamaha like Kawasaki produced their own engines however the larger market share they enjoyed allowed them more financial freedom. They could afford to produce models intended for racing which drove up warranty costs that other makers simply couldn't afford to. The situation with 1982 SRX production being held up and the eventual arrival of the 1983 V-Max is evidence Yamaha had to change it's marketing strategy with the economic times as well. Paying wages to American production workers in Lincoln, Nebraska to assemble Kawasaki sleds had to add to overall production costs. Same would apply to Polaris. These are just a few points to consider regarding your question.     

[Shawn]

Do yourself a favor and set aside the design differences between vintage sleds. They are only design/engineering differences. None of them alone make for a better or worse snowmobile. What really matters is the complete package and how all these differences work together. In that respect Kawasaki did a wonderful job. If you spend the time to remedy any issues your Invader has to make it reliable for riding enjoyment I assure you it will not disappoint you. In sound mechanical condition your Invader is one of the most trail friendly sleds made that also offers exciting performance. Before modifying the engine be sure it has good crank seals, the carbs are clean and properly adjusted and the clutches are working as they should. Then ride it and see if you can stop smiling afterwards ?   

[invader87]

it is possible to put a reed cage on virtually any piston port sled. their is however a fierce debate on the performance gain. in stock form i believe it would offer no advantage. trying extreme porting with EXTREME blowback like i tried on my orange sled a reed cage may prove useful. reed cages on piston ports seems to be kind of a fad that i see come and go. i know a couple of oval guys that have never used them and recently there has been talk from each one of them putting them on. it seems when one guy does something like that everyone tries it. It was even shown on the homepage of vintage sleds a set of cylinders and reed cages adapted to it as a "super secret" project. (polaris free air cylinders i think. cant remember)

[invader87]

those pesky srxs run with huge porting and huge power. they also run very easily with that porting. they just got the magic combination i guess. i pretty much copied srx porting on the orange sled and she is a bear to tune and just to keep running below 3000-4000 rpm while a ported srx will sit there and idle. amazing stuff.

[Shawn]

Now that I noticed your Polaris jackshaft post I get this sled will be raced. If you're allowed to lose weight then do all you can to. The Polaris clutches offer the most parts selection and ease of tuning. They will likely be your greatest opportunity to increase the sleds performance along with gearing. More so than engine mods. Be mindful the Kawi piston port engine cannot rev as high as a Rotax. Kawi had it giving about as much power as it could without being a grenade. The 440 SRX made immense power at the expense of reliability. The checkered flag only waves at the end so be there to finish. I watched these "vintage" sleds compete as a boy when they were "late model". Beware the sleds may be vintage however the speeds today are not. If you can tune the TMX flatslides they offer more peak performance than roundslides @ the expense of fuel economy. When properly tuned the throttle response is like EFI. If the porting is on the wild side and it must idle @ 5,000+ rpm's then why not let it so long as the clutch doesn't engage yet ? Less time to the 9,200+ rpm power peak. Sometimes you gotta make the most of what things are rather than dwell on what you wish they could be. This is one of those times regarding the Kawi engine. You can run with those other guys but you might have to work a bit smarter to do so. Focus on those clutches and the gearing soon as you have the engine well tuned. Wish you success and more importantly lots of fun doing it. 

[wildwolf]

Often reed valves are thought to increase peak performance but in fact the opposite is true, reeds increase the bottom of the powerband by helping balance the port timing up to 5,000 rpm range where everything balances out and the power builds. And turning a 440 kawy much past 8,000 rpm is a tuff deal because of the crankcase volume, you have to have a balance between that and your port timing and volume. The SRX has a larger crankcase volume so it responds better to performance mods. Both are GREAT sleds, but the KAWY is my favorite!

[gixxer6]

True, just adding reed valves won't increase peak hp.  But an engine with reed valves can run more radical porting (aka more peak hp) and still have decent low/mid power, where a piston port motor with equally radical porting would suffer in the low/mid. 

[wildwolf]

True, just adding reed valves won't increase peak hp.  But an engine with reed valves can run more radical porting (aka more peak hp) and still have decent low/mid power, where a piston port motor with equally radical porting would suffer in the low/mid.

Isn't that what I said?  My point is the crankcase volume is the real limiting factor in the kawasaki engine for max horsepower, no matter how you port it or high you rev it can only flow the volume of the crankcase. Any engine is still just an air pump, the bigger the pump the more air and fuel you can fill the cylinder with and that equals horsepower.   

[wildwolf]

From this page with dyno results from AAEN and it sounds about right. I would agree with Shawn get it set up the best you can, clutchs,gearing,seals and carbs. Seems like a lot work and expense for 6hp?(About $ 1000.00 for pipes&carbs and more for porting) Yes porting will help in the hp, but it will become more difficult to keep tuned and would actually be quicker more of the time with just a good set up. If your going to race it you could gain that much HP by just dropping some weight(seat,lights,gutt the hood,handlebars,etc.) and lose maybe 10-15 pounds? Then ride it and SMILE! Aren't sleds FUN?!! 

http://www.torysvintagesleds.com/enginesperformancespecs--adv.html

1978 - 1981 Kawasaki Invader 440
Engine:


Kawasaki 436 cc Water Cooled
Single Plug Twin


Tuned Pipe
36mm Mikuni Power Jet carbs


 Performance:


Stock Set-Up / Horsepower @ RPM   (Factory Claimed)
67@7800 -  8000 RPM


Horsepower w/38 roundslides, stock cyclinders and AAEN pipes
69.6 HP @ 8000 (AAEN Dynoed)


Horsepower w/38 flatslides, stock cyclinders and AAEN pipes
73 HP @ 8250 (AAEN Dynoed)

[gixxer6]

Often reed valves are thought to increase peak performance but in fact the opposite is true,

Sorry, I must've misundstood what you were trying to say. 

[sprocket]

I spun my engine @ 9800 Rpms all day long on a piston port stock rods on the dyno it made good power with the right Combination you can get over 100hp & be very reliable race gas only though. Aaen will tell you flat out his mod pipes are safe verses the other guys. Yes the porting is small compared to Yamaha. I've seen so many put reeds on their cylinders only to get beat by us piston port engine guys this all depends on what kind of racing you do & your driver. For an example a Kawasaki that makes mid 90's in hp the right set up & driver say ice ovals can do very well in super mod. Remember what racing you're going to do most sleds you see look factory but they are not they have today's Technology in them, some chassis are heavier than the stock ones because how the rules are written.

[wildwolf]

Sproket, I'am in the process of building an Invader for mod snow oval racing out west. Basically wide open engine with era correct suspension with rubber tracks. Which motor are you getting the 100hp with, the 4/6? I have several early Invaders and a couple 4/6 motors, and a vari-ride suspension and that is the combo I was thinking about using.(Early Invader,4/6 motor,Vari-Ride) And maybe changing the cooling system to a better heat exchanger and losing the radiator,big fuel tank,clunky seat, etc. The tracks we run are groomed hard pack snow that gets very tore up by the mains, so I was thinking about a Camoplast Ice Attack track.  Is my thinking OK? Any tips?

Thanks
WildWolf