Snowmobile Racing

I'm not trying to argue with sucess, sounds like a great twin piped engine combo. However, the single pipe on it obviously wasn't working very good. What I'm saying is there are guys like Rich Daly making single pipes for 180 degree firing 2 stroke engines (twin cylinder) that make as much power as any twin pipes at the same rpm. When Rich gets a single working at let's say 8500, compare it to all the twin pipe sets on the same engine, and you will find they don't make any more power, unless they rev higher.

   I'm NOT saying that you can build a twin cylinder engine with a single pipe and win Pro Stock at 8500rpm, since the one off twin pipe sets by the best builders will continue to make the most power and win at 9000rpm. I AM saying that my experience and many other's in the past 20 years have convinced me over and over that a single pipe two cylinder is an doscile over-achiever, especially in limited traction conditions like snow. I've built multiple identical twin cylinder sleds in the past, one with single, one with twin pipes, and even though the twin pipes did make a handful more power on the dyno at a couple hundred rpm's more, the twin piper would NOT consistently beat the single piper in the snow. That makes twin pipes not worth having in the snow to me!

    Glenn Hall brought a 1200 D&D Cat twin to DTR and made 226.7hp @ 7500 with a single pipe, and then installed matched twin pipes to make 235.1hp @ 7800, but the twin pipes still only made 225.2 @ 7500. I know which I'd rather have, especially when tickets are handed out in NY left and right for exhaust. The top single pipe builders know exactly what's going on at the top of the exhaust ports on a 180 degree firing 2 stroke engine!

   Airflow & flow bench data, been there, only to find out that it doesn't mean much on 2 stroke cylinders, since transfer port sucess is controled by pressure-drop expansion, charge availbility, and most importantly timing. Flow has little to do with pipes, also.

I know you're talking about race motors, I am talking about trail motors. Ron tried several trail single pipes on his motor with the goal of keeping the rpm's under 8000 so the crank would live. Everyone told him that the crank wouldn't live at over 8000 rpms but he still tried running it on the trails running over 8000 rpms and ended up with his crank in 2 pieces in a very short time. I see twin pipes outrun single pipes on the same motor all the time. There may not be more than a 10hp difference on some motors, but clutching to get that extra 10hp makes twins worth it. I'd never run a single but I run a triple so it doesn't really matter to me. I've seen totally done up D&D motors on the dyno..not nearly the advertised hp unless you get one specially done. Why do you think you see a ton of 1010's, 1147's and 1200's for sale? The only 1200's I've seen run are sprayed or turboed...on the trail of course. I've seen lots of pissed D&D motor owners. Ron has fixed a lot of D&D trail motors including motors out of stock cylinders and motors out of D&D cast cylinders for the trail. Heck, he reported the D&D 1107 I bought so it would finally make some power and he had to fix the o-ring grove in the top of the cylinder because it wasn't deep enough and ate a couple of o-rings before we looked at it closer. He has a D&D cast triple port 1132 in his garage right now that is just a mess from D&D that he has to fix. But I do have to say their 1000 triple ported motor does what it advertises..i.e. 185-190hp and run a ton of miles with zero problems. When engine building if you're limited to available pipes on the market (and not 1 off pipes) you have to work with what is available for a trail motor to keep rpms low and exit through a stock can. Air flow means a lot when you know what you're looking for, where and when. All I know is that when we go to local "run what you brung" races and guys are all there with their race sleds, Ron is right near the front against sleds in the same cc range with his trail sled.

I'll keep it simple,

LRM,  Larry is partial to the 700 twin for making power and as far as SLP pipes- they use some of LRM's stampings.

Might be worth it to speak with Mr. Rugland about his pipe stampings.  

I would have to disagree with the trail motor and rpm thing i have have 2 trail sleds that ran more than 8000 one ran 8400-8500 in an 800 and the other ran 9000 with no issues on either. And as for your pissed  D&D motor owners that dont make the power. The only clear answer would be to take it to them to tune on the dyno. After all they created and would know were to go with it.But if you look most of there off the shelf motor kits and or single/twin pipes arent really meant for race they are a big bore trail and that is not a purpose built race motor...just my 2 cents

Having the crank true and welded is a great way to start.

   Longshot, I am from the Rotax world, as I believe you are too, where the only reason to limit rpm's is for clutch efficiency. Nearly all catastrophic Rotax lower end failures are related to fatigued pistons, not RPM's. Polaris guys have suffered common catastrophic rod pin and pto end failures for years, somewhat related to poor quality control of align honing the cases. Measuring two case cores that I just got in for this quad build, one varries .002 from one end to the other!

   My last two trail sleds that I built were a 1050 triple Rotax in a ZX  that was from a old 780, we logged over 10,000 miles on this 73mm STROKER that ran 8600rpm's at 224hp on a conservitive dyno, with 52mm carbs and custom in house carb tuning components. The current is an 8500rpm Series III 800 with 6000 miles logged so far who's hp is confidential at this time. The only engine maintainence is new pistons every 1500 miles and one set of reed petals on the triple. I hear the same things all the time about what's trailable & durable, and what's not. Different approaches & designs yield different results. These are trail sleds that go on 250 mile rides in 1 day and burn 30 gallons of gas to do it. Want to see the gas receipts? Not the typical "ride it 15 miles-race-go home" sleds. Everyone has a reason to believe what works for them, doesn't mean it's the final answer, can't we all just agree to disagree?

   I've seen the pistons D&D is using in the big twins, they won't hold up to trail riding, not all their fault, I know guys trying to run them, they colapse to mega clearance in no time. Fine for a well maintained drag sled, don't ride it if you want it to perform after 100 miles. Quit lookin' at the pistons, they will look fine, throw your compression gauge in the garbage, it means nothing, measure the skirts & leak down check your engine about 30 degrees before and after TDC and you will see what you really have. A piston that should be used for an ash tray after 100 miles.

Martin You are right about the Wiseco/D+D clearance thing.My buddy picked up a 1010 Twin that cut itself in half.He was going to use the good cly and piston.When we measured it there was .018 clearance.Piston looked fine.Blown cly was cut in half. 

longshot racing:

And as for your pissed  D&D motor owners that dont make the power. The only clear answer would be to take it to them to tune on the dyno. After all they created and would know were to go with it.

So you're supposed to buy a motor for $3,000 or more which they have been selling for years and they should know exactly what it takes to make it run and then spend another $300-$500 just to dyno it to find out the RPM range it likes to run at and how much HP is makes?

Dr.Crank:

Having the crank true and welded is a great way to start.

All of the cranks he puts in his twin or triple motors are welded and trued.

Blaine:

longshot racing:

And as for your pissed  D&D motor owners that dont make the power. The only clear answer would be to take it to them to tune on the dyno. After all they created and would know were to go with it.

 

So you're supposed to buy a motor for $3,000 or more which they have been selling for years and they should know exactly what it takes to make it run and then spend another $300-$500 just to dyno it to find out the RPM range it likes to run at and how much HP is makes?

    I'm not an advocate for them, I bleed yellow and somewhat blue now, not green. However, I do know a guy who had a 1010 that was having issues, and they put his sled on thier dyno over a year later to help sort out his issues, and didn't charge him.

   Why not go to the source when you have issues, just tell the source you ain't payin' 'cause you've paid enough.

   I know another guy who had big twin from a different big name builder, he had nothing but troubles, after working all season with them to try to sort it out, they ended up giving him a full refund and new stock core parts in exchange.