coffman Pipe on 750sxi

Ryan Stewart

Ryan Stewart

Location
Idaho
So i was playing around with my carbs. and i noticed my arm wasnt fully opening the needle. I used a flat nose screw driver to pend it up a bit, and now the needle actually pops out and in normally. The way i had it... it wasnt even budging a milimeter. now it moves a small bit. Maybe that was all my issue was, it wasnt giving a big enough burst of fuel, which is why i could ease it into a full throttle.
 
Ryan Stewart

Ryan Stewart

Location
Idaho
So, good news. it seams to run well. flexing the needle housing up only slightly seamed to have done the trick. I also moved to a 95 size low jet. But for some reason, my WOT feels like 70% power. But rather than tinkering with it, im going to take it all out, because its SOO DANG LOUD. i mean.... its.... very loud. To the point where im extremely emberaced at the lake.

So if anyone wants a freshly painted, nicely welded coffman rocket pipe that has water hoses and limiter already installed... Give me a message and Ill work out shipping with ya.

I think im going to throw money at it at this point and get that 755$ Factory pipe and call it good. Theyll at least have instructions and screw sizes to where I wont have to tinker much. Or ill just go back to stock, but i have to find 2 things... A new water box, and a new hose leading to the left size that has the correct bends. (I cut mine, like a duffus)
 
W

Work&Play

Location
Lake Mead
Did you ever get this figured out? I am running the same setup and my ski rips and is not terribly loud at all. I am running a different water routing then you though and I think that my be why yours is so loud? Check to make sure you don't have any air leaks in your fuel system. I had a split in my fuel regulator which is on the top of my fuel tank and had many of the same systems you are having. I blew (gingerly) into the vent tube and could see and hear where the air was escaping and realized if air could be blown out then it could also be sucked in as well when the ski was running making it impossible to tune. I am running duel stock kiens with 7/8 turn out on the bottom jets and 1 and 3/4 out on the tops and running a stock 800sxr impeller. It is probably a bit over propped but I love the mid and top and it fits my riding style. Just FYI
 
Ryan Stewart

Ryan Stewart

Location
Idaho
curious. my fuel mechanism on top of the tank... did have a hole in it. But i remember determining that hole was actuall a function of the devise. I blew into the hose and i heard air leaking, so i put some water down in there and saw bubbles. But when i cloggd it with glue, i was not able to blow from the 'return' line which connects into the fuel mechanism. I found out thats where the 'return' line returns fuel into your tank. and the two hoses that go into the tank are both fuel 'feed' lines. Am i maybe incorrect on this?
 
W

Work&Play

Location
Lake Mead
One of the hoses is a vent tube which normally goes up the handlepole, If you have the stock mechanism which I believe you do? If you blow into that vent tube and see any airleaks around the plastic nipples where the other tubes attach then you have an airleak and you will never be able to jet correctly. I figured this out on my ski when it suddenly started falling on its face down low and my primer wasn't working properly. When I would use my primer it would suck air. That is when I blew into the vent tube and heard and saw bubbles exiting from one of the nipples where my fuel line, reg and reserve lines and return line, attached to the top of the tank. I threw that out and ordered a billet one from one of the mfg and my ski returned back to running normally, once I undid all my jetting changes from trying to fix it with the airleak.
 
Ryan Stewart

Ryan Stewart

Location
Idaho
That sounds like my issue. Sadly i bought a new TDR waterbox and went back to stock. I havent tested it since ita snowing now. Guess if stock does the same thing ill know exactly where to start. So you just blew into the handle pole hose, while everything is hooked up elsewhere and looked for leaks? Makes sence. I unhooked hoses and carb locations and blew and it all seamed okay. But ya... my ski was so loud, i was emberaced to give it gas.
 
W

Work&Play

Location
Lake Mead
yes, leave all your fuel lines hooked up and just blow into the vent line. You should hear the leaks if you have them and probably smell fuel too. Mine was leaking where the line went into the plastic nipple that made a 90 degree into the fuel tank. I think if you route your water differently you will quite that badboy right up too. Not stock quite, but not obnoxiously loud either. PM me your number and I can share with you how I routed my lines. I dump alot of water in the pipe and my pipe never gets sizzling hot or anywhere near that.
 
anthonystempak

anthonystempak

Location
Fortwalton Beach Fl.
Dude
Your
Ski should run pretty good find a after market milled head 180psi is gonna be another 3-4mph gain and big seat of the pants feel

Another thing dude l forget what prop you have ,but you should start with skat 9-17 ,them balancing and sharpening and if you feel repitching

Your ski is a 50-60mph ski

If your at 70℅ ,the bottom and midrange feels good , its either rich or lean on the two top screw adjustments or still off high jetted for your altitude
 
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Ryan Stewart

Ryan Stewart

Location
Idaho
I think its 135 on compression. And id love to look into new a new impeller. Id appreciate specific recomendations, or knowledge. Im not sure of what different numbers. mean or their benefits. Bottom range was fine, mid range sometimes didnt grab and stalled. And WOT felt like 80% speed. It felt pretty bad. I messed around with 3 sizes of springs, up to 95 L and up to 135 H. Couldnt get it right. And im sure it was how it was water cooled. I had a water regulator at the stinger and the rest to a pisser. I think the muffler was on backwards from other peoples, but i dont think that would matter. Either way, i went to stock and a TDR. Ill get to play around next summer. Possibley attempt the coffman one more time. Only reason i bought a tdr is because i grinded the stock one out to rip it out of the hull. Oops.
 
Ryan Stewart

Ryan Stewart

Location
Idaho
okay, ill snag that. Question though.. my current fuel setup has 1 return, 1 supply, and it looks like the dual carb has a cross line connecting the two, instead of each having their own supply line.

With this new fuel tank pickup, should i utilize the two supply lines? and if so, i wouldnt know really how to hook that up properly. And if so, do i need to change anything internally to the carburator? new jets or sizes. I already have a variety of sizes
 
anthonystempak

anthonystempak

Location
Fortwalton Beach Fl.
Holmes time to order a basegasket and mail order a drill hone ,and some rings , 25-55$ bucks ,its probably the reason why it wont run right ,your low on compression 150psi is stock and you want 165psi to 175 ,

I would order a wiseco 200$ forged light kit with the gasket kit its time to rebuild and either a super lightweight lightened flywheel , or a dales total loss except there not making the triggers rightnow on backorder msd will run for 1hr dales draws less than half the amperage 1.5-3amps so a 16amp battery will last awhile
 
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