changed exhaust now boggs down and cuts out...please help

tfaith08 said:
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.
Click to expand...
If i have a leak will replacing all seals fix tha problem
 
tfaith08 said:
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.
Click to expand...
If i have a leak will replacing all seals fix tha problem
speedyslyder said:
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?
Click to expand...
Im not sure i bought the blaster about aweek or two ago n the piston n rings where shot so i had the top end rebuilt. Had stock exhaust. With no silencer on it but exhaust was cracked and had holes in it so i bought a used exhaust and silencer so i dont know what its built for no mods to air box jus lid on
 
your problems are this.
top end,air leak,and not a big enough main jet.
If it is rebuilt properly with no air leaks and correct main jet,and air to fuel ratio screw is set proper then it will ACTUALLY LAST THIS TIME. 32-1 MIX LOL..
 
speedyslyder said:
your problems are this.
top end,air leak,and not a big enough main jet.
If it is rebuilt properly with no air leaks and correct main jet,and air to fuel ratio screw is set proper then it will ACTUALLY LAST THIS TIME. 32-1 MIX LOL..
Click to expand...
Thats what mix ive been using
 
I would replace the seals since your in there. Then when you wait jet your carb. Before you start your blaster leak test it. If there are no leaks, torque everyrging. Do heat cycles and ride it not guning on the throttle. Then plug chop to confirm jetting. Once good you are ready to rip.
 
http://www.motosport.com/atv/oem-parts/YAMAHA/2002/BLASTER

www.rockymountainatv.com

you dont have to buy from here but at least browse to see the OEM parts available.

year calculater pic plus ex1 1 1.jpg
 
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Head,cylinder and wats left of piston lol
 

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That is one serious case of perfect detonation, even the head is fried.

A complete rebuild may be the order of the day.

I bet you a penny to a pinch of deer droppings that the cases are punctured .
 
A blind man could see that the head needs resurfacing and bellying out, I can see at least 2 spots where a gasket would struggle to seal.

It looks like the top of the bore has excessive ring wear.

Any cylinder with all the crosshatching reamed out by a sloppy piston should be rebored.

What brand of measuring instruments did your builder use?

Your piston shows signs of being extremely hot, so hot that the incoming fuel charge from the forward transfer ports, has cooled the metal causing crystallisation and destroying the crown.
 
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