Which is faster?? The srx 440 or the 540

[chrisrider63]

I have the 86 v-max with cut pipes and polaris clutches on it. It was all ported up and I blew it up in febuary. My dad is an old yamaha mechanic so just have to get him in the right mood to build it again. I also have a 81 440 project on the go with a 83 vmax bottom end I think i may also re-build the bottom end.

[vmax-540]

Hi Bob.. Yes I have worked on a lot of these engines over the years. I used to work in and even owned a automotive machine shops. We used to do work to a lot of sled engines from boring cylinders, carbs, installing sleeves, cranks, and re machining heads, I don't want to sound like a know it all because I am not,but I have had a lot of time inside engines.
I have had a Vmax sense about the time they came out and the biggest problem they have had is when Yamaha came out with them they were pig rich, they came with 330 main jets.Yamaha quickly came out with a service bulletin to change them to 290's and they ran well. That was in the early 80's and around the time all sleds came pig rich,so a lot of people thought that if 290's were in there then we can jet down to 270's or smaller like all the other guys with other sleds were doing and that was when they would blow pistons. The 290's were real close to right on as long as you watched the temp and altitude then you were OK.
As far as the porting goes,and I don't confess to be a port master but I have done porting to these engines the "Update Porting" does work well. No I haven't had it on the dyno but Yamaha claimed it would add about 8.5 HP to the 540, Dyno Tech did a pipe shoot out and confirmed that claim,it is in the article index so you can see the results ,it also shows that the stock pipe is about the best you can get ,even for that porting. Pay close attention to the shape of the transfers that is critical . Your friend probably knows more then I do about porting ,but I don't think that the stock port is to wide. If I measured it correctly then I come up with 52mm wide port and most performance shops say about 65-70% of the bore size ,so that is in the ball park. The one thing I do know and I hope you don't have them is back in the early 80's there was a company (or guy) selling sleeves for these engines that were junk, the ports were either way to small and you had to do a lot of grinding to make them fit the liner or they were the right size but nothing lined up and you had to do a lot of grinding to make them work. One other problem with them is they were a different diameter the LA Sleeve or Advance sleeve so if you wanted to remove them you had to call L.A. Sleeve or Advance Sleeve and have them make over size sleeves, I hope you don't have them ,If you do that may be the reason for the wide exhaust port. I hope this helps .

[chrisrider63]

I think the snow bug bit us all september is getting close prime time for working on the machines when its cooler out. Everyone really put alot of get replies and ill enjoy putting together the 440 I think

[Bob Vehring]

Thanks Jeff. The sled I bought just had the engine done by a "pro", yes I've heard that before The owner could not get it to start, simply opening the cap on the gas tank told that story. I cleaned the carbs, flushed the tank, and it fired right up. After idling for about two min. I heard it louse a couple hundred RPM. Pulled the pipe and could see light scuffing on the skirt, pulled it down and only had a thou and a half piston to wall, so much for the "pro". Didn't know until I asked here that stock they didn't have sleeves. We build engines for the 120's and karts full time so have milling machines and lathes here. Damage isn't bad
We raced alot, but it was 20 years ago so a little rusty on the big sleds. Everything I have learned about this sled, has come from this board, what a great place.
I am pretty good with jetting and all the sleds have EGT's Have boxes of tuning parts for Miikuni's. Got my SRV down to where I can keep it between 1150 and 1250 any temp from 0 to 30 by just using the needle. Will probably put together a set of non Power jet 38 and start with that set up. All I need now is time

[Undertaker#13]

all my win's with the VMAX go to the thanks of TIM BENDER! I met tim at a local grass drag tn 1990, and asked him for some advice. Tim wrote down how to set it up and the VMAX has never missed a beat from that day! I have a good picture of the VMAX with all the trophy's it was won, but it won't down load!

[opsled]

Any of you guys from S.E. Wi.?

BURLINGTON (30ish miles SW of Milwaukee). Chocolate City, Home of ankle grabers and bleep bleepers.

Why ya wanta Fight My dogs faster than your dog ya know

Naw seriously. I'm just off Hwy 36 on the north side of town. I've got 8? 10? maybe 12 I'd have to look) 81's and Vmax 540's in the top of the barn. If ya need something or want to come down to shoot some bull give me a call 262-767-9023.


Phil (opsled)

[Undertaker#13]

opsled hunting for a 1984 VMAX throttle block that isn't sun faded

[jims68]

I have read alot about this debate and from old timmers heard stories about this matchup but now that we have two complete stock sleds I have seen the differences first hand. The 81 is a lighter, peakier old school type of sled and with a little clutching pulls like a madd freight train all the way up to its 100 plus range. But it has problems also. The sled needs ALL of the updates to work properly. The comet clutch is one of the best updates but make sure it is a Yamaha Comet because the faces of the clutch are angled different. The stock butterfly carbs work great but are a pain in the arse. Starting is choke till it pops off then DONT use it again. They are also a pain to get synced and don't touch them after you get them set. Give it a little gas and it starts right up. Do this when warm also. Sled took a full tank of fuel to wake up after overhaul. As with any re-build make sure the crank is nuts on for trueness. VERY important in this sled because of the long PTO snout and important in all sleds for longgivity. I was told once buy a old racer don't even set the crank down without it being in the cases. Just setting it down on the table can get it all out of wack. The VMax we have is a 85 that looks allmost showroom. Guy had Aaen pipes on it and ran it with old gas in it. Had to completely re-build it also so we put it back to stock. Runs really well now since we re-built the fuel pumps because the old fuel ate out the diaphrams. Weighed the two sleds and we have a 85 pound weight difference which computes out to about a ten sled length difference apples to apples setup. The VMax has way more low end grunt but with the added weight and un-studded realy gains it nothing in a lake race. Like others have stated in a 40 to 60 mph kick down it is a non race. The SRX just pulls away. We were in Waconia for the show last weekend and had a good running 570 Exciter and a piped and and very good running SX Exciter which everyone knows ran well stock. The VMax was a non event to the two Exciters but some of that being we haven't ran a tank full of gas through it yet to break it in. The SRX would be even with the stock Exciter at all races and the SX a couple ahead of both from a dead start and a rolling start. The SRX would pull away from the Exciter and pull even with the SX after about 500 feet then start pulling away. One of the 16 year old's with us said he buried the needle on the SRX at 110 mph and I have had it to 105. Now figure these speedo's were calibrated at 80 and are off from there 10 to 15% you are stll at 95 to 100 mph and I know we were going faster then that. Had a couple of 05 06 Cat 440 Sno Pro's try us also and it was a non event. The one followed us around for a while and raced us again because he could not believe it. We were told when we bought the SRX from the original owner that it was fast and was set up by the dealer he bought it from. The weights in the clutch are notched and modified comet weights. Not sure which ones they are anymore. Also make sure to mix your gas 50:1 also. The stock carbs have a lean spot in the mid range and these high strung motors need the extra oil. Good luck and have fun with these sleds like we have. People sure take a look when we are out with them.

Jim

[chrisrider63]

Thanks for the info, where would the 85lb weight difference be at?? The skid?? The bigger pipes ??LOL That is a crazy weight difference I didnt think there would be a huge difference like that..WOW. Ive heard guys putting stock slide carbs on dont get as much HP out of the "if tuned right" butterfly carbs. Also I talked to Justin from the site here that had the srx and he said the SRX 440 crank, the SRX 500 crank and the 540 crank are all the same volume. So I was gonna just take a 540 bottom end and build this motor. I wanna have some good stories to tell about racing guys with new machines lol.

[vmax-540]

jims68 You are Spot on in what you said in your post. I have heard of a lot of 81's hitting over 100 mph on the lake . Here is a link to a Speed calculator if anyone wants to find out the top speed of there sleds,just enter the values.As I have said in other posts I have both sleds and have know reason to lie ,and I don't like saying anything bad about my Vmax, but I will make it VERY clear the 1981 SRX 440 is faster than any Stock Vmax.The Update porting Vmax with some gearing changes and good studs on good ice will probably beet the SRX, The Update porting is about the same port lay out as the 81 & 82 SRX ,and form what I was told by a Yamaha tech years ago the 81 SRX was 88 hp. The 82 SRX 500 was 92 hp and the update 540 was and confirmed by Dyno tech in this site at 96 HP.
http://www.cmsaracing.com/calc.htm

[chrisrider63]

Gessh maybe ill just port out the 540 and put the engine in the SRX , wouldnt that be a monster...

[vmax-540]

Port the 540 and install a tooth or two on the top and Ya you would have a fast sled..

[chrisrider63]

The update porting really puts the HP at 96HP?? So it adds on 16 HP to the stock 80??

[agfirecat]

Ive got an 81 and an 83 and i havent got to line em up together yet. but im gonna get them on the lake together one of these weekends.our lake just got nice for riding . im gonna put fresh studs in both of them. my freind has a radar gun and well get the results. with video for youtube. In my opinion i think the 440 will take my v-max they may look the same but themotors have adifferent attitude from one another.the 440 reminds me of the tasmanian devil and the 540 is more like the roadrunner.and they both run great. the only fault my 540 has going for it is it has a 108 clutch on it . the 440 has all the updates done to it. and it has the 102 clutch that may give it the advantage.i will post up with the result.and video for you guys

[vmax-540]

Hay agfirecat I like the Tasmanian devil ,roadrunner terminology,but you hit the nail right on the head ,that is how they feel like.I take it you got the SRX back running. Thats good hope to see you at the Whiteout,looking forward in shooting the breeze with ya..