Yamaha Blaster Top end rebuild (DIY)

[usamahmoola]

Hi guys! I'm new here.. I've got a 06" Blaster and i need to rebuild the top end, I've sent my cylinder to the machine shop and the guy said it seems fine so it will NOT need to be bored. So i bought a 66.00mm (stock size) Wiseco piston and i need to drop it in. It's my first time doing this so i would really appreciate some advice and tips etc..
And also how to i torque the cylinder? Could anyone suggest a good torque tool that will get in there!

Thanks

 

[Awk08]

what was the reason it needed rebuilt ?
broken piston skirt ?..... low compression ?
if one of those /\ reasons....it needed bored to at least the next over size.
if not one of those reasons...it didn't need rebuilt.


remove the fuel tank and pipe and a reguler torque wrench with an extension will reach the head bolts.

some use a crows foot attached to the torque wrench on the base nuts..............

http://www.harborfreight.com/7-piece-3-8-eighth-inch-crowfoot-metric-wrench-set-94427.html

 

[usamahmoola]

what was the reason it needed rebuilt ?
broken piston skirt ?..... low compression ?
if one of those /\ reasons....it needed bored to at least the next over size.
if not one of those reasons...it didn't need rebuilt.


remove the fuel tank and pipe and a reguler torque wrench with an extension will reach the head bolts.

some use a crows foot attached to the torque wrench on the base nuts..............

http://www.harborfreight.com/7-piece-3-8-eighth-inch-crowfoot-metric-wrench-set-94427.html

View attachment 28025

Note sure exactly what happened as i bought the bike like this. A very small piece of the piston is broken off.. the cylinder does seem fine and it has been honed. Oh yes, does honing affect the bore size?

 

[Awk08]

skirt breakage is usually a result of piston slapping around in a loose bore.
I'd bet real $ that if the piston was wore to that point, so is the cylinder/bore.

is this a reputable shop that told you it didn't need bored ?
he needs to bore/hone to that exact piston size, not just hone it, let you buy a piston and hope for the best.
yes honing can take thousands off the final size of the bore.


if you have the piston and the honed cylinder now ?
measure it, with feeler gauges,
or with a micrometer (piston) and a bore gauge (cylinder bore) and report those measurements here.

both methods shown here...........

report your findings

 

[Lyndle]

Have you found the piece of the piston? If it's floating around in the ports or the crank case you could have much larger problems.

 

[usamahmoola]

Have you found the piece of the piston? If it's floating around in the ports or the crank case you could have much larger problems.

No i haven't came across it. It's a very small piece though, it's the piece between the two openings on the piston (the reed cage side).

 

[usamahmoola]

skirt breakage is usually a result of piston slapping around in a loose bore.
I'd bet real $ that if the piston was wore to that point, so is the cylinder/bore.

is this a reputable shop that told you it didn't need bored ?
he needs to bore/hone to that exact piston size, not just hone it, let you buy a piston and hope for the best.
yes honing can take thousands off the final size of the bore.


if you have the piston and the honed cylinder now ?
measure it, with feeler gauges,
or with a micrometer (piston) and a bore gauge (cylinder bore) and report those measurements here.

both methods shown here...........

report your findings

My new piston (Wiseco 66.00mm) does not fit into the cylinder, however my old piston (stock standard Yamaha 66.00mm) slips into the cylinder and still has slight play. Now I'm really confused!

 

[usamahmoola]

Okay.. now it seems like the bottom of my cylinder is abit smaller then the rest. If i put the piston in from the top of the cylinder, it slips in easily, however when it reaches the bottom it gets stuck!!!
Please help!!

 

[jbuckster07]

This is a perfect example in my opinion why you should not just replace a stock piston with a stock piston.... The reason your old piston has slight play is becuase both the piston AND cylinder wall have been worn down.

Also, just becuase you ordered a 66mm piston does not mean you are getting a 66.00 mm piston, its next to impossible for that to happen, you could have got a 66.05, 65.94, 66.11 ect... Read the numbers stamped on the piston.

What you should have done, ordered a 66.25 piston, WAIT for the piston to arrive at your door. Take both the piston AND cylinder to a REPUTABLE machine shop and have them bore the cylinder to match the piston.

 

[usamahmoola]

This is a perfect example in my opinion why you should not just replace a stock piston with a stock piston.... The reason your old piston has slight play is becuase both the piston AND cylinder wall have been worn down.

Also, just becuase you ordered a 66mm piston does not mean you are getting a 66.00 mm piston, its next to impossible for that to happen, you could have got a 66.05, 65.94, 66.11 ect... Read the numbers stamped on the piston.

What you should have done, ordered a 66.25 piston, WAIT for the piston to arrive at your door. Take both the piston AND cylinder to a REPUTABLE machine shop and have them bore the cylinder to match the piston.

I've already received the piston. Take a look at the size.

 

[rshutchinson]

The cylinder is out of round and/or is tapered. If that new piston has play then you already know it's not going to work. The cylinder is too worn.

If a machine shop ever used the words "seems fine" I'd never go back.

I'd go to a different machine shop, ask them to measure the top, middle and bottom of the bore. They should measure multiple areas for taper and roundness. Then see if you can return or exchange that piston for the piston in the next oversize from whatever the largest measurement they give you. Then take both the cylinder and piston to them and they will bore to fit the piston. Or just send it to KORacing and be done with it.

 

[usamahmoola]

The cylinder is out of round and/or is tapered. If that new piston has play then you already know it's not going to work. The cylinder is too worn.

If a machine shop ever used the words "seems fine" I'd never go back.

I'd go to a different machine shop, ask them to measure the top, middle and bottom of the bore. They should measure multiple areas for taper and roundness. Then see if you can return or exchange that piston for the piston in the next oversize from whatever the largest measurement they give you. Then take both the cylinder and piston to them and they will bore to fit the piston. Or just send it to KORacing and be done with it.

Thanks! I really appreciate your guys help! I've finally managed to find a decent machine shop and this guy told me to change my piston to a 66.50 (2nd available oversize) and he says that I'll have to go as much as that to get it cleaned up!

So hopefully they'll change the piston for me..
And we'll take it from there.. once again, thanks guys!
Will keep you guys posted.

 

[usamahmoola]

Heyy guys.. hope you guys are good!

I need some help! I've rebuilt my top-end.. but now when i try to start the bike, it only kicks from half way through the kick start. So the first half of the kick is like play, it only catches after half way and the bike doesn't start!

What does this mean?

Thanks

 

[CrazyDave]

Heyy guys.. hope you guys are good!

I need some help! I've rebuilt my top-end.. but now when i try to start the bike, it only kicks from half way through the kick start. So the first half of the kick is like play, it only catches after half way and the bike doesn't start!

What does this mean?

Thanks

Did you get this figured out.? What was it ? Sorry I've been reading throughout these threads gathering knowledge and I am very interested to know the end result.