Hi, I have an '01 DS650. I have had it for only a short time, and since I bought it I have been fixing and replacing parts and getting it running well. I finally have it running perfectly. I had a chance to get out with my buddy and run some trails, it worked great on the trails, engine runs beautifully. Here is my concern:

I have 22" rear tires, so to help get a little more low end I put a 15T front sprocket and kept the 40 back. I used a GPS and found my top speed with a hill and a tail wind was under 90 km.h, or about 55 mph. I thought this was far to slow. In addition to that, as good as it is running, my buddy was able to beat me off the line with his Honda 250 ATC!!!!! what gives! I am a very good driver, and had higher expectations with this machine. With my current gearing and setup I expected to at least hit the 110- 120 km/h range, and outrun at least a 30 year old trike.

What could cause it to run like this? The engine SEEMS perfect! in 5th gear, my revs are maxing out at around 5000, never gets higher than that.... carb is jetted, everything tuned up.... no idea what to do? ANy help or advice, please provide.... Im stuck on this one. Thanks

 

you got big problems if you think its running good and its only seeing 5,000 rpms ....

stock rev limmit is around 7,200 I think and most cant stand that and replace the cdi to get 8,200 rpms or better on a stock motor ... stock you should see 75mph or so ... my baja X is running 9,300 rpms and 90mph .....

 

Those ATC250R's will beat a lot of things off of the line, and further down the track! That's not what I would be concerned with. With 22" rears you need a 42t rear sprocket to compliment your 15t front. Probably have a torque beast but you sound like you prefer speed. Have you done the OMR stock carb mods? What CDI are you running? Your gearing and tires will affect your RPMs but you shouldn't be bouncing off of the rev limiter at 5K.

 

I know something isnt right... based on the sprocket to wheel ratio etc the charts say I should be able to do 75 mph with my current setup, and i do like the high end speed because I do a lot of dirt roads and such.

I currently have stock CDI, no carb mods apart from a 127.5 pilot and dynojet stage 1 kit, because it was running lean before. I dont think I am hitting a rev limiter, it just seems like its doing all it's got... If I run it down a hill I can get the m higher....

The ONLY thing I am skeptical about is my muffler... The stock one was smashed, so I welded in a large tractor muffler.... It is a straight through muffler, so not a lot of restriction, and is pretty loud too, so I dont feel like it is holding me back any, and I have jetted accordingly with a 185 main.

Im running 91 OCT fuel.... brand new UNI filter, closed airbox etc etc. I was considering putting my 16T front sprocket back on, but then I figured I should still be faster than 55 with what I have....

Still not sure where to go from here.

Thanks.

 

quote ( so I welded in a large tractor muffler. )

That tells me alot ... 55mph is 45mph faster than you should ever go .. you cant fix stupid

 

Bartmann, I have to disagree with you there, it is not stupid, it is ingenious, or perhaps creative, but not stupid. I dont have the $250 + dollars required to go out and buy a state of the art silencer, and so I was innovative enough to produce a very functional product that silences very well, and looks professional. I dont plan on racing this machine ever, and I have put 3 hours of hard trail riding on this bike, and it worked fantastic, so please hold back when you have the urge to make offensive comments simply because I dont have the finances to afford the best of the best. I thought I did a pretty damn good job.

Now if someone may be able to explain to me why my silencer would be able to rob my bike of 35% of its top end speed, and about the top 2500 revs, then pleas do enlighten me, as I am eager to get to the bottom of this problem. And at this point I am open to any advice that does more than insult my intellect.

Thanks

 

I think it very possible that your exhaust is the culprit but unable to correctly tell you the reasoning. I can only guess that it's a lack of back pressure not allowing scavenging....but take a better qualified persons advice to chime in.

 

Many tractor mufflers are straight through but have large louvers punched into the core to diffuse the sound. This design causes a lot of turbulence and poor flow and also does a poor job of sound control.

What was the core of the tractor muffler diameter? I have seen 2.5 inlet tractor mufflers that the core is only 1.75 after you factor in the louvers.

Using an alternative muffle is not necessarily bad, just really research what you are using.

 

Using your brain can do wonders, 75% or better of ds owners change there pipe to a performance pipe. what percentage of them people do you think give a rats azz about there stock pipe ? 10% maybe. So asking for a stock pipe is like asking for a soda. someone will help you out and ship you a pipe for less than a fast food lunch. stock pipes are easy to come by. And most jump at helping others out. fix it right and you wont be on this forum pulling your hair out guessing at problems. If you cant afford to fix it you cant afford to ride it. save up and fix it right. sorry but welding a tractor muffler on is just dumb. If I cought my son doing doing something like this I would smack him up along side his head and ask him if he's f-ing retarded.... He would learn quick and not do that again.

So how to fix your problem ? Ask who has a stock pipe there willing to hook you up with ?

 

with mufflers there are several issues you have to take into consideration

1) they must provide a certain amount of air flow AND create a certain amount of back pressure

this being said if its not producing the back pressure you are robbing your performance. if its a straight pipe with no resistance yea it sounds cool being all loud but are you getting your full potential out of fuel, performance, RPM etc.

2) provide a quieter ride

3) does it have a spark arrestor in it if not be careful riding in dry areas of tall grass and leaves and some trail systems will not allow you on the trails without an arrestor

so there are some thoughts for you to think of does that muffler do all these things? in my opinion NO some things can be short cutted some things can not and the safety and performance of using a muffler not designed for your quad can create other issues that will cost you WAY more in the long run than buying an original part