changed exhaust now boggs down and cuts out...please help
- Thread starter jtmoney61585
- Start date
I looked up mikuni jets n this place that was selling them was the same ones selling the kit 6Sigma..i had to give make model and all mods so Shouldnt they give me mikuni jets
If you ran a stock jet with an aftermarket pipe that called for a larger jet, I can assure you that a re bore is in order.
Choose your piston, give it to your machinist and he can bore to suit the piston.
Make sure the ports are chamfered and OEM or Cometic gaskets are used in the rebuild. Some gasket kits come with green paper gaskets, refuse them.
Leak test the engine, re jet to suit the pipe, at least a #280, perform heat cycles, re tension the head and cylinder and ride 2 tanks of fuel at no more than 3/4 throttle.
Plug chop to confirm jetting, if all good grip and rip!
Choose your piston, give it to your machinist and he can bore to suit the piston.
Make sure the ports are chamfered and OEM or Cometic gaskets are used in the rebuild. Some gasket kits come with green paper gaskets, refuse them.
Leak test the engine, re jet to suit the pipe, at least a #280, perform heat cycles, re tension the head and cylinder and ride 2 tanks of fuel at no more than 3/4 throttle.
Plug chop to confirm jetting, if all good grip and rip!
Not trying to be rude, but I'd recommend that you stop before you do anything else. You can spend a lot of money by just ordering parts, not to mention if you order the wrong parts and the distributor won't take them back. When you say that it was smoking from everywhere, it scares me. That's never, ever, EVER a good thing.
If you Google Mikuni jets, you'll find all kinds of places that sell jets to fit a Mikuni. That doesn't mean that they're genuine Mikuni. I'd consider that jet kit a bag of emergency only parts. Go to a Yamaha dealership and tell them that you want 260-300 main jets.
First order of business is to post a picture of the bore and measure it. Wait on someone to tell you whether you need it to be bored or not.
Don't order a gasket kit from anything other than OEM Yamaha or Cometic (like Blaaster said). If you shattered, broke, or did whatever to the piston, you need to split the cases. Not doing so will result in endless rebuilds until that is done. Aluminum destroys aluminum, so if pieces of your piston are in the bottom of your cases, you'll eat pistons until it's all out (which could be many, many rebuilds along the way).
I'd also recommend that you post pictures of the dome because detonation damage is possible.
The short answer is to send the cylinder, head, and a few hundred bucks to KOR and let it be his problem. He'll set you up pretty well and you don't have any guess work there. Next, split the cases and clean the crankcase. Replace any bearings that don't look brand new and replace all seals while you have it apart. Reassemble the bottom end as per the manual (which is on this site). Do a leak down test, install a 290 or 300 main jet, needle in middle position, screw at 1.5 turns out, install a UNI or OEM filter WITH OIL, check all of your electrical (again, reference the manual), run heat cycles, do a break-in (KOR will recommend both the heat cycles and break in procedures if you sent the cylinder to him), do another leak down test, pug chop, adjust jetting as necessary, plug chop to confirm. With the exception of sending it to KOR, none of this is optional. If you don't follow these recommendations, which are going to be the same as those of others, you are destined to go through this again.
The price of doing a proper rebuild is roughly what it costs to do a hack of a build twice. Do it right and postpone the next rebuild by a considerable amount of time.
If you Google Mikuni jets, you'll find all kinds of places that sell jets to fit a Mikuni. That doesn't mean that they're genuine Mikuni. I'd consider that jet kit a bag of emergency only parts. Go to a Yamaha dealership and tell them that you want 260-300 main jets.
First order of business is to post a picture of the bore and measure it. Wait on someone to tell you whether you need it to be bored or not.
Don't order a gasket kit from anything other than OEM Yamaha or Cometic (like Blaaster said). If you shattered, broke, or did whatever to the piston, you need to split the cases. Not doing so will result in endless rebuilds until that is done. Aluminum destroys aluminum, so if pieces of your piston are in the bottom of your cases, you'll eat pistons until it's all out (which could be many, many rebuilds along the way).
I'd also recommend that you post pictures of the dome because detonation damage is possible.
The short answer is to send the cylinder, head, and a few hundred bucks to KOR and let it be his problem. He'll set you up pretty well and you don't have any guess work there. Next, split the cases and clean the crankcase. Replace any bearings that don't look brand new and replace all seals while you have it apart. Reassemble the bottom end as per the manual (which is on this site). Do a leak down test, install a 290 or 300 main jet, needle in middle position, screw at 1.5 turns out, install a UNI or OEM filter WITH OIL, check all of your electrical (again, reference the manual), run heat cycles, do a break-in (KOR will recommend both the heat cycles and break in procedures if you sent the cylinder to him), do another leak down test, pug chop, adjust jetting as necessary, plug chop to confirm. With the exception of sending it to KOR, none of this is optional. If you don't follow these recommendations, which are going to be the same as those of others, you are destined to go through this again.
The price of doing a proper rebuild is roughly what it costs to do a hack of a build twice. Do it right and postpone the next rebuild by a considerable amount of time.
Has anyone noticed this recently? People posting threads and then not responding or listening to us? Seeems like its been happening a lot recently.
My machinist says the bore is fine jus needs to b honed an the head is fine also...will post pics later today
when you change exhaust you need to tune carb again.Is the pro circuit built for low to mid,or mid to high?
Did you modify the airbox?
It sounds like the exhaust was part of the problem,since no bigger jet was installed but if your top end fried then that is more of the problem know
Fix top end then put a bigger main jet in, and of course no air leaks because it makes the engine run much hotter then it is supposed to.
Did you modify the airbox?
It sounds like the exhaust was part of the problem,since no bigger jet was installed but if your top end fried then that is more of the problem know
Fix top end then put a bigger main jet in, and of course no air leaks because it makes the engine run much hotter then it is supposed to.
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