SRX 1108 Race Sled Buildup

Yes, those cases are huge. They come stock with a 76mm crank.

It still makes good power at 265hp on Iantomasi's dyno, and is very reliable. I am going to work with reed spacers of various thickness to help acquire some more case volume. Also, I did plumb the intakes for nitrous......
 

hey ryan i was wondering iff you had a set of carbs for a vmax i think there 31mm but 33mm would be better i would imagine and also i got a set of heavy hitter weights that weight in a 48 grams but i think there to heavy for my sled to pull what do you think i think the stock weights are 40 grams.
 
valin said:
I am back from the dyno. We found a few issues down there, but none of which were causing my issues. Gerry also loaded it up for an 8 or 9 second run on two of the passes, and we could not get the motor to lay down. Therefore, the issue is not in the motor, and things are continuing to point to the possibility that pressure is being created under the hood when travelling down the track, which is pressurizing the carbs, resulting in a very rich condition, and causing the motor to lay down part way down the track. Simply venting the carbs up by the handlebars will fix this, if that is in fact the issue.

It is hard to compare the power it is now making because he has changed his dyno setup since the last time I ran this motor down there. The dyno is now reading somewhere in the neighborhood of 3-4% lower than his previous setup. My motor produced 261.x hp a few runs while we tested various things, which, in comparison, would put it in the 270hp range on his old setup, so there is some improvement in power over the last time I dyno'd it. If I were on another dyno such as down at Dynotech, I probably would have produced in the 280 hp range because his setup reads higher, or if I went to Jaws, it would have read lower. However, that isn't what I was trying to do.....I needed to compare gains from previous numbers.

Iantomasi still figures it should make more power than it is currently making. He things that the motor doesn't have enough case volume with the small Yamaha crank cases for the 83mm pistons I am running, and wants me to pull it apart and measure the case volume. If that is correct, and the case volume is too tight, there could be more power to be made. :)

All in all, it was a successful day. We found a few small issues, and the motor came home running, so I am happy.
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Valin, We also found issues with motors that would lay down at high mph. We had some exhaust leak (very small leak). It was making it's own EGR system under the hood at speed. Seemed like a air box problem but wasn't. Had to seal every part of the exhaust and the outlet to make sure none could come back under the hood.

Good luck this year!
 
t-rav said:
hey ryan i was wondering iff you had a set of carbs for a vmax i think there 31mm but 33mm would be better i would imagine and also i got a set of heavy hitter weights that weight in a 48 grams but i think there to heavy for my sled to pull what do you think i think the stock weights are 40 grams.
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The heavy hitters will work fine. I do not have any carbs for a v-max.


toydoc said:
Valin, We also found issues with motors that would lay down at high mph. We had some exhaust leak (very small leak). It was making it's own EGR system under the hood at speed. Seemed like a air box problem but wasn't. Had to seal every part of the exhaust and the outlet to make sure none could come back under the hood.

Good luck this year!
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That is quite interesting. I always use Ultra copper to seal all of my exhaust joints, but that's certainly something to keep in mind.
 
I made a few changes to the sled for this season, and all will be for the better.

I completely removed my entire lube system, and sliders, and am going to run a wheel only setup. I picked up 4 sets of 3.25" wheels from Wahl to throw in the Proline skid, and removed all of the stainless steel wear plates that the sliders normally run on.

I removed 48 ice pics, for a total of 144 now, instead of the 192 I had to run last season because of the wear plates.

I cut the carpet track down to 10.5" wide.

I switched back to 10 tooth plastic drivers. The 11 tooth billet drivers were too big, and were potentially causing a pivot point and ski lift.

By doing all of this, I was able to remove 10.6 lbs of rotating mass from the track alone, and an additional 5 lbs from the rest of the lube system. The sled will now weigh in at 399 lbs, full of fuel and coolant, ready to go, down from the 414 lbs it was last season.

I am bringing it out for testing with 25/37 gearing, which is only geared for 150 @ 1:1, but I'd rather start low and make sure everything is good. If all goes well, I'll be running installing 26/36, which will gear me at 160.3 @ 1:1. I have always found that gearing for 5% overdrive has always worked out best for me in the radar runs, so that should bring me right into the ballpark, again, if all goes well. Pray to the gods of speed for me :)
 
If you can, run the exhaust out the side or bottom and seal around the pipe as it goes through the pan. May want to seal off exhaust side of the hood to make sure none gets pulled in at speed. At 100 plus odd things happen as you know. Air moves and pulls.

I like the plastic drivers best. I'd also bring lots of Armor All and put it all over the drivers and inside the track. You wouldn't believe how much the drivers hold on to a track under power.

Run few 25/37 for bast line mph. Then I'd easy up on the clutching, take some weight out of the tip (or helix finish). Shoot for the last 100' to let the rpm walk up 200 rpm past what it was. See if the motor likes the rpm to make up more mph at the end, I been seeing lots that do. I think at full speed sometimes the clutches just sit and look at each other, hold same rpm like a stand off. So I use the rpm to keep them moving / working.

Sorry if I talk to much. Just stuff rolling around my head...
 
I have also pretty well decided that this is going to be my last year of snowmobiling. I'm starting to lose interest, and will be either selling this sled, or parting it out at the end of the season. I will also be selling my 780 trail sled.
 
valin said:
I have also pretty well decided that this is going to be my last year of snowmobiling. I'm starting to lose interest, and will be either selling this sled, or parting it out at the end of the season. I will also be selling my 780 trail sled.
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that's kinda what i've been thinking too. my bro's viper lost a mag rod bearing this year and my srx lost the center rod bearing tonight. so, i think i'm gonna get out of it as well. my bro is going to sell his sleds off now and be done and i'm sick of spending the money as well, as its a real expensive sport. not to mention that i don't like being out in the cold much anymore. i've also lost some interest and ambition for the sport. i would like to give my banshee some more attention, and repaint the chassis and all like you did on your build. well, enough of me talking. good luck ryan in this year's radar runs.
 
Doing some track dyno work tomorrow to get it ready for the races this upcoming weekend. Perhaps I will post results. :)
 
all good things come to an end.Like mopar said..I to am starting to lose some interest also in the sport.It is to expensive to keep on top of things..parts are going up in price,gas is going up also..but the worst of it is the cold.I am starting to hate the cold weather more and I stay in more then ride the sleds.Good thing I never bought a new sled and wasted my money away.Once my sleds start to fall to pieces or blow up..that'll be it...I'll ride for fun on warmer days..but won't go nuts out there when the cold stuff hits.Getting older now and more important things to spend $$ on now...When I was younger it was a different story..but it was cheap in them days cost of sleds and gas.I am almost at $1000 on gas already this season and like nearly $3000 on parts and stuff..that is to much.Don't really know the future of sledding as gas will continue to climb and sled prices never go down..good luck to the manufacturers and more laws and people trying to stop or ban snowmobiles....
 
Pfft. You guys want a little cheese with that wine. lol. if you want to play you got to pay. lmao
 
Well I'm back, and have some work to do. The initial warmup 1/2 pass went fine.....ran it up to 120 mph or so just to check wash and temps....all ok. We rolled into it pretty slow, had some slight belt slippage on the bottom, but nothing too drastic, and it peaked in the mid 130's for hp, which was pretty decent to start with. Then, all hell broke loose, and by hell, I mean the track. On the second pass, at 137 mph the track decided it was outta there, and completely grenaded, leaving it's mark of destruction on my tunnel, bulkhead, and my in-tunnel brake setup. I am quite thankful that I was running a track with no pics or chisels in it, as that would have probably destroyed my chassis. Needless to say, I have some straightening to do.

No worries, things like this happen. I will be heading back on the track dyno again next week.
 
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