Ok yesterday I modded my own end cap, thought I would try it out before buying the mr horsepower cap. On the top end I gained 10 mph, it seemed to have more power, snappier feel. Plus mine has the factory spark arrestor. All this with no carb or other engine mods, so hopefully it will make a great addition to changing jets and setting the needle to correct position. The way I modded the cap was pulled it off and cut off the two outlet tips, then ran 2 horizontal lines with a cut off wheel, one above the tips, one below. Then took a hole saw and went down with the edge of the saw on the outer side of both tip welds. Then all I had to do was use a die grinder and ground out until I was at the edge of the spark arrester. It leaves an oval opening but spark arrestor is still intact and it really opened up the exhaust. If anyone has any questoins let me know.

 

That sounds like a good idea to increase flow while keeping the spark arrestor. Wish I had though of it before I butchered my spark arrestor. I removed the spark arrestor and left everything else intact. That improved things a little, but without making too much noise. Besides, if it got to a point where it would shoot a flame through the whole pipe and spit out those two little holes I would be in too much pain to care about forestry regs. However, I did order one of the Mod Quad end caps to further increase the flow. It looks great and has the same dimensions as the Mr. HP one but for much less cash. I know Mr. HP did a lot of research, but I need to look out for my wallet too. And with the Mod Wuad you can choose the finish you want. I am interested to see how your quad responds after jetting. Keep me updated. And by the way those were very clear and conscise instructions. I am sure anyone wanting to use you idea as a model will have no prob doing so.

 

When I modded my end cap I had to go one size smaller on the main, it went rich... go figure.

 

Rich[img]i/expressions/face-icon-small-confused.gif[/img]

That is weird, I was wondering that if the airflow out of the end cap u modded was causing turbulance in the can could that create a higher back pressure and as a result lower air flow? not a fact only a thought , But it would be hard to imagine anything being more restrictive than the stock cap

 

Not trying to start a flame war but, there is no way possible that you gained 10mph on the top with a end cap mod. A stock machine tops out at around 78mph +/-. This is because the factory gearing and rev limiter won't let you go any faster. You just get to a certain RPM in 5th gear and ping off of the rev limiter thus limiting you rpm's and therefore your speed. Change the gearing such as a larger front sprocket and or raise the rev limiter and you can achieve higer top speeds. Unless you change you rev limiter it is impossible to go faster than about 78mph with stock sized tires. I noticed that you have 22in rear tires which serve the same purpose as a smaller rear sprocket or a larger front srocket. But still you would only gain about 3mph on top end with 22inch rears alone. 5-6 mph with a 17T front sprocket and stock sized 20in tires. I just think you might be mistaken about you speed changes and I hope this will help.

 

Ok here it is, with 22 inch tires and stock gearing with my trail tech speedo i went down my flat, gravel road in front of my house, I would never hit the rev limiter and speedo would get up to 85-90 mph before i modded the cap, usually 87 is all it would do. Modded the cap and went on the same road and hit 96 mph and it would not gain much more. With that you cant even argue that the speedo is off. Tested before with same speedo, same conditions and after the mod it was 9-10 mph more, same conditions as before when I made the pass. I was running right at 7900, 8000 rpms and never hit the rev limiter. With 22 inch tires and stock gearing and stock endcap I cant remember hitting the rev limiter once in 5th, all I could only get up to about 7800 rpms quickly, yes im sure i could hit it if i ran it a mile, with the modded endcap I could get to 7900-8000 much quicker and with no problems in about a 1/4 mile or under, not sure on the distance for sure but before I could not reach those rpms or speed in the same distance.

 

ARE YOU SURE YOU HAVE YOUR SPEEDO SET RIGHT. I HAVE A 2004 DS BAJA X & CAN ONLY GET 73.1 ON MINE. I USED GPS & SPEEDO LIKE YOU HAVE. I THINK YOU HAVE THE WRONG TIRE SIZE PUT IN. I HAVE 22 IN TIRE , 17 TOOTH FRONT SPROCKET, THE SETTING FOR THE TIRE SIZE IS 1755MM I THINK. RECHECK THAT.

 

Im not positive that the speedo is correct. I actually measured the tire and programmed it that way. Im not really believing that it goes 97, just that it did gain 10 mph from before and after with no changes except for the mod cap. Either way even if the speedo is off it would not affect the gain. Just top speed mph might not be correct. Main reason I got the speedo is to keep track of ride time and odometer more than the speed. Which if it is off a little that will throw of those, but Im not to worried for now.

 

DO YOU LIKE THE END CAP. HOW DOES IT SOUND. CAN YOU FEEL ANY DIFERANCE

 

It sounds awesome, very compairible to the pro circuit t4 I think. Maybe not quite as loud, but real deep raspy sound to it. It really seems to give it a little pep.