1979 SRX 440 Performance Tips?

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pitcrew

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I'm going to grass drag this beast, and was wondering if you fellas knew of any additions, other than a port job that would quicken it. Of course a pipe would help, but not sure if the rules allow. Has anyone had luck with an offset key, head rechambering, carb tricks, different clutch weights etc. Can I get different chain-case gearing (500 ft track)? I find with the piston port design, it's a bit of a dog at low rpm, so it's going to need a good stall. I've built fast mini quads, but this is a different ball-game!
...Thanks
 
sure, gearing is available, something around a 2.00-2.10 is good for 500 ft small motor sled, these sleds use the old triple row roller type chain. Definitely clutch weights and spring changes, you will want a 6000 rpm engagement with a srx440 on grass, usually you will need to notch the weights. Use a comet clutch 102c on it and save yourself a bunch of headache by not using the old yamaha primary. The problem comes with the secondary clutch as there was only 2 helix's ever made for that secondary. I used a conversion jackshaft in my old 440 and ran a art. cat secondary clutch. Aaen wild race Pipes help with race porting, 40-44mm carbs and lots of compression 180+ lbs. You can achieve a decent gain by lightly cutting the heads, you can only take a light haircut off them as they have offset combustion chambers and require machine work to really chop em down to get into good race compression. Removing airbox and running pod filters and shortening up the intake runners on the cylinders will give ya a boost in performance. Timing is adjustable on the old srx by moving the stator plate in the slots provided. Add wheels to the skid and remove the hyfax so it doesnt drag on the track.
 
Thanks for the replies boys!
Deano, I'll keep that in mind. What advantage are the 8f-200's? The porting? Mrviper, are there issues with this engine as far as dynamics, as why do they use a 1 3/4 lb plate just outside of the flywheel? Can this be removed (and spacer installed) for the sake of less rotating mass for grass drags? Is the secondary a waste of time with the limited helix selection, even for just dragging? K&N or Uni? Any wheels in particular for the skid?
Sorry for all the quiries, I'd just like to know this thing a bit better.
 
that weight on the end of the flywheel is a trail kit, yamaha did that to get the crankshaft out of the torsional vibration/harmonics section of the rpm band, it made the float bowls foam up leaning out the engines and added to rapid clutch wear on trail sleds, you dont need it on a race sled for 500ft. you can remove the flywheel weight then the spacer ring off the waterpump/recoil housing and it will all go back together agin

k/n are good filters

you can do....ok, with the secondary, at least get a new secondary spring it will be plenty tired from age. I may still have a secondary and the other helix that was available from my old 79 drag sled, I will have to look, I also have the helix angles wrote down somewhere too.

I used the wheels and mounts from another junk skidframe and added 3 or 4 to each side on the rails, just drilled the holes and mounted the stock wheel mounts on it, worked great.
 
GET ENGAGEMENT UP TOO ATLEAST 5500. I CAN TELL YA THOUSAND THINGS TOO DO, BUT I DON,T KNOW HOW FARR YA WANT TOO GO OR WHAT RPM YOU WANT TO RUN THIS MOTOR AT !!! 3:16 (tony)
 
It will be primarily for grass drags...possibly the odd blast on the lake, but as it has about 3mm of suspension travel, I'll keep it out of the bush. I'd like something that still has good reliability, yet something to compete with some quick sleds, with one possibly being an SSR. I can't remember what it wound out to (stored for 5 years) so I'm guessing high 7's, but is say... 9000 RPM a reasonable number? I'm new at this engine, so open to recommendations.
I'd be pumped to hear even just 900 of your ideas! Hints like ignition improvements would be great. I'm seeing 8k4 on other threads as a boost to RPM. Is this the route to go? On a tank sticker it recommends 15/1 fuel mixture. Of course this is pre-synthetic days, and as we run Opti-2 in our race quads at 60/1, is this about the same to run in the SRX? I'll stop now and let you talk.
Thanks
...Mike
 
MIKE, 9000 IS STOCK RPM. NOW THIS OF CORSE IS WITH STOCK CARBS, PORTING, PIPES etc. NOW, YOUR RIGHT 15:1 WAS 26 YEARS AGO. YOU CAN PROBLEY RUN 32:1 WITH TODAYS OIL AND OF CORSE USEING REAL REAL GOOD FUEL. FORGET THE 8K4 STUFF, EVERYTHING YOU HAVE WILL WORK FINE. THE BEST PERFORMANCE GAIN ON THESE SLEDS WAS COMET CLUTCH, BIGGER CARBS, PORTING, AND DEPENDS AGAIN WHAT RPM YOU WANT TO RUN. NOT TOO STILL VAGUE, BUT WHATS THIS SLED HAVE DONE TOO IT ALREADY, PRETTY HARD TOO SEE A SRX THAT NEVER BEEN TOUCHED. 3:16 (tony)
 
I bought it from a guy who owned it from new. He said it was bone-stock, and he couldn't fix the handle on a pail, so I know he couldn't do anything to it. Should I stay with the Mikunis or go a different route? Again, I'm open to RPM suggestions. Our mini quad engines run 13,000, but that may grenade the poor SRX.
...Mike
 
I found a extra secondary clutch, both helix's that were available and a new yellow yamaha secondary spring for it. $50

I also have a 79 service manual from mine and it has all my gearing,jetting, clutch specs written in it.

have porting specs and dimensions that came from Olav Aaen, I had him do a 440srx for me and a set of race pipes and thru talking with him and sitting in thier trailer one year at the world of ice series he gave me all this stuff to run on my sled, his clutching sheets, jetting and it has pics of all the porting and where to do what and all, I really dont want to get rid of it but would pass some of it on to you.
 
I don't think I'll need the secondary as mine is fine. Other than that, I'll take anything that would help. As larger carbs are the consensus, what would you go with? I've had good luck with Keihin D-Slides and Lectrons. Are the stock pipes sufficient with a porting and carburetion, or are the Aaen's a must? I may not be able to run pipes in a certain 600 class, but I'm checking. Let me know what you'd want for all your treasures you'd part with.
Thanks
...Mike
 
Mrviper, I just talked to the racing fella from my Yamaha dealer who had a big grin when I mentioned Olav's name, so I gather he's THE GURU of tuning. I don't mean for you to part with anything that's near and dear to you, but any of his specs as well as parts etc. I'll buy. I'd big time appreciate it as it would save me hoards of research and leg work! You can e-mail me at mikesquads@shaw.ca
Thanks
...Mike
 
Hmmm...no reply, I guess I must have offended him.
Tony, what do you recommend for larger carburetors, round or flatslide, or something else?
 
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