rich or lean????

[Blaster200boy]

I dont think that my blaster is lean but when im riding, it takes a while when i give it full throttle to actually hit the powerband. When i hit full throttle it goes a long brapp and it finally winds up. I think it maybe rich. i have a 340 main in and the needle is on 3rd slot from top (stock).pilot is 32.5 and 1.5 turns out. i live in floyds knobs Indiana, across the river from Louisville Kentucky. i think the elevation is 900ft above sea level....btw, i have a toomey b1 pipe and stock carb except the jets. have eight 1/2in holes drilled in airbox and running a uni filter....

 

[little3mil]

prob masking a air leak with fat jetting, have you ever done a leak test? you need to anytime you have the reeds off or topend off. if its giving you a hard time jetting it then more than likely you have a leak. click the link at bottom of my sig

 

[Blaster200boy]

I think i now know why its doing this. ive got two missing head studs. one in front of cylinder and one in the back....machine shop said he could fix it for $45

 

[yb200]

fix that and take the airbox lid off

 

[Whitty21]

if you wanna check if its rich just take the lid of and go for a little rip, just not long incase it makes u too lean. If that fixes it its lean, bet definately get that fixed. And what do you mean by head studs, the bolts? and are they missing or broke off?

 

[Blaster200boy]

if you wanna check if its rich just take the lid of and go for a little rip, just not long incase it makes u too lean. If that fixes it its lean, bet definately get that fixed. And what do you mean by head studs, the bolts? and are they missing or broke off?

Missing.unfortunatly, im in the process of selling it.....

 

[Whitty21]

take another one out and just go to a nut and bolt store and ask for one, they will prolly have it, if not your local yamaha dealer will

 

[Blaster200boy]

well, i took the time today on my day off work to pull the cylinder off. What i found inside was looking normal until i looked at the piston. I took some pics to show you guys what i saw.

depending on what people think will make me decide if i wanna sell my 400ex and keep my blaster....

Is this a normal looking piston? i know the top of the piston is from having a front and rear missing head stud....

Let me know guys.
Thanks

 

[Erwin8r]

That doesn't look normal. Looks like it got real hot, and maybe scored the cylinder walls. Screw the pistons--how does the cylinder look? Your rings? Any head pitting or obvious deformation of the combusdtion chamber?

 

[Blaster200boy]

That doesn't look normal. Looks like it got real hot, and maybe scored the cylinder walls. Screw the pistons--how does the cylinder look? Your rings? Any head pitting or obvious deformation of the combusdtion chamber?

The cylinder has matching scars. you cant even feel the scars on the piston or cylinder. the head looks fine

 

[Erwin8r]

Matching scars but you can't feel them? You might be able to get away with a re-hone and new piston/rings... But you will have to replace those two things, at least. I'd also check your rod for play...

 

[Blaster200boy]

Matching scars but you can't feel them? You might be able to get away with a re-hone and new piston/rings... But you will have to replace those two things, at least. I'd also check your rod for play...

rod is fine. 1mm bottom end play. perfect...

 

[nd jat]

Side to side or up and down ........side to side is fine but up down you shouldn't be able to feel that play in the rod, if the bearings are good.

 

[Blaster200boy]

Side to side or up and down ........side to side is fine but up down you shouldn't be able to feel that play in the rod, if the bearings are good.

no up and down play whatsoever. There is 1mmof side to side play. i think once i sell my 400ex, i will deff eiher buy new rings or piston. im running 32:1 and a 340 main with stock 32.5 pilot 1.5 turns out. stock needle clip position...

 

[sicivicdude]

340 main sounds really fat for the mods... I'm running a 290 and the chops are dead on but I know I don't have any air leaks.

How many hours did that top end have on it and what is the current bore size? It seems to have an awful lot of blow-by down the side of the piston. Normally you wouldn't see that much unless it was slapping (which could account for the intake bridge being scored but no metal you can feel on the cylinder) from being too far out, or had about 1,000 hours on it and the rings had lost tension.

Did you say you had studs missing? Which ones because that could have something to do with it...

 

[Blaster200boy]

340 main sounds really fat for the mods... I'm running a 290 and the chops are dead on but I know I don't have any air leaks.

How many hours did that top end have on it and what is the current bore size? It seems to have an awful lot of blow-by down the side of the piston. Normally you wouldn't see that much unless it was slapping (which could account for the intake bridge being scored but no metal you can feel on the cylinder) from being too far out, or had about 1,000 hours on it and the rings had lost tension.

Did you say you had studs missing? Which ones because that could have something to do with it...

I think it had not even 10 hours on it. theres a missing stud in the back. and the one in front was up there but had no nut because everytime i tightened it, it kept pulling out. i thought it might be better just to leave it alone...i'll prolly throw a new Wiseco 67mm piston. its only $90 plus a base gasket and some Yamabond.

 

[sicivicdude]

plus the cost of two new studs and a helicoil kit...

Rings don't seal from spring tension... they seal from gas pressure pushing them out towards the cylinder wall. If the head is allowing gas pressure out because the head gasket isn't crimped properly, you're loosing compression and the rings aren't working right. You could not have been able to break it in properly with two cylinder head studs missing.

If you're buying a new piston, measure the current bore to make sure a 67mm is the size you need. I suspect that you're looking about 67.15mm actual bore size which is too large for a 67mm piston. You'll need to order a 67.25 mm piston and have it bored to accept the new piston. A new bore is usually around $50 at a local machine shop so it's not really adding to the price too much BUT it will stay on there longer than 10 hours...

and when you put that new top end on LEAK CHECK YOUR MOTOR. Either build a leak checker or purchase one. No need to burn up that new motor when $15 in parts at home depot will save it.

 

[Blaster200boy]

plus the cost of two new studs and a helicoil kit...

Rings don't seal from spring tension... they seal from gas pressure pushing them out towards the cylinder wall. If the head is allowing gas pressure out because the head gasket isn't crimped properly, you're loosing compression and the rings aren't working right. You could not have been able to break it in properly with two cylinder head studs missing.

If you're buying a new piston, measure the current bore to make sure a 67mm is the size you need. I suspect that you're looking about 67.15mm actual bore size which is too large for a 67mm piston. You'll need to order a 67.25 mm piston and have it bored to accept the new piston. A new bore is usually around $50 at a local machine shop so it's not really adding to the price too much BUT it will stay on there longer than 10 hours...

and when you put that new top end on LEAK CHECK YOUR MOTOR. Either build a leak checker or purchase one. No need to burn up that new motor when $15 in parts at home depot will save it.

Ive already got the head studs heli-coiled. It was $45. Guy also told me that i needed a new piston and that the 67mm would work just fine. he said a little hone got rid of the scratches.

 

[sicivicdude]

Who is this "guy" that you speak of? nah, just playing.

If a light hone took care of it and the bore is good to go, woodward specialties will cut you a deal on a new wiseco piston.

Just make sure you do a leak check on it and jet it accordingly. With the mods done a 340 should be pretty rich. If it's not and you don't smell and gear oil out of your exhaust, you might want to look into a stator side seal.

 

[Blaster200boy]

Who is this "guy" that you speak of? nah, just playing.

If a light hone took care of it and the bore is good to go, woodward specialties will cut you a deal on a new wiseco piston.

Just make sure you do a leak check on it and jet it accordingly. With the mods done a 340 should be pretty rich. If it's not and you don't smell and gear oil out of your exhaust, you might want to look into a stator side seal.

Machine shop dude. lol