Am I going to have to rejet

[heyketz]

Bought a $275.00 Blaster that isn't running. No compression so I pulled the head and jug to find out the piston is toast and the jug is scored. Taking the jug in to be bored and honed for a Wiseco 67.25 piston kit. Am I going to have to rejet the carb after the piston kit is in or should the stock jets work without messing with the carb. I know DO A LEAK DOWN TEST!

 

[brandoz28]

stock jetting should be fine, as long as everything else is stock. just plug chop after break in to verify.

 

[Quadrider10]

should be fine i think..... but y bore it all the way out???? thats such a stupid idea, unless that is the only thing u can do.

 

[yamaha28]

any aftermarket parts?

 

[brandoz28]

should be fine i think..... but y bore it all the way out???? thats such a stupid idea, unless that is the only thing u can do.

i'm guessing since he said bad scoring, that it'll have to go that far just to fix it

 

[heyketz]

Completely stock blaster except oil injection has been removed. Shop looked at and measured jug. Said to order a 67.25 piston kit. Ordered a Wiseco top end kit on Ebay for $112.99. Includes 67.25 piston, rings, wrist pin, topend bearing, circlips and all gaskets. Not my STUPID idea it's what has to be done.

 

[yamaha28]

Jetting should be fine then, a leak probably made the top end go boom. Leak down test when you get it back together.

 

[heyketz]

thanks to one and all

 

[Quadrider10]

yup yup^^^^^...........................................

 

[*Quad*King*1986]

i agree... jetting should be fine since it is pretty much a bone stock blasty. good find though! I gotta start paying more attention for these good deals lol

 

[Blaaster]

It could be a good idea to open up the carb and just check what main jet is in there, and the needle setting. The previous owner may have messed with it.

You said the piston is toast, and as mentioned this could be caused by an air leak, but things like float level, dirt, ignition advance, , the list goes on.

I would be at least pulling that carb apart and checking and cleaning it.

Wait on, you said oil injection removed, has it been run at 32:1 ratio and on what oil, and has the oil injection nipple on the carb been sealed up?

 

[heyketz]

carb oil injection was sealed with a small screw in the end of a little piece of the oil injection tube on the carb nipple. don't know ratio previous owner was using for premix.

 

[Blaaster]

carb oil injection was sealed with a small screw in the end of a little piece of the oil injection tube on the carb nipple. don't know ratio previous owner was using for premix.

Should be sealed with a little cap and a sealant, screws in the plastic oil line have been known to let some air in.

There must be a reason why the piston was toasted, or did it just wear out.

Were there any signs of crystalisation of the aluminuim on the piston crown?

Is is possible to post a few pics of the piston?

 

[heyketz]

Re: Am I going to have to rejet - PICTURES ADDED

Pictures of the piston and cylinder

 

[Larry's Shee]

I would clean the nipple out good and spooge it with 3bond or silicon

 

[Blaaster]

The pic of the piston sugguests to me that it has been run somewhat on the lean side for a while. The cratering towards the centre of the piston is also concerning.

I repaired a motor for a chap the other week, that had taken off his air cleaner cover, and had run it for 3 weeks without re jetting.

He would have only had to have changed the main jet one size to have been safe, but he did not realise he had to, so he paid the price of a new top end.

As to your Blaster, Is the air box lid still on, is there a filter in it and is it a stock filter?

What plug is in it? What main jet is in it?

When you re fit your top end, be sure to do a leak down test, check your needle and jetting.

I dont know where the bike was from previously, but if the guy had ridden it in very cold temps without re jetting, that could have cooked the piston.

 

[heyketz]

Air box lid is gone. I asked the previous owner if he had it and he said there wasn't one when he bought it. Running a stock foam air filter. Plug is a NGK B8ES and the tip looks like the piston top kind of white and pitted. Main jet is a #230. Carb is apart and soaking in a gallon can of parts dip. It stopped running last fall and has been sitting in his garage all winter.

 

[brandoz28]

I would go up a size if there's no airbox lid!

 

[heyketz]

I will replace the airbox lid as soon as I can find one.

 

[Blaaster]

Just as I thought, air box lid gone, #230 main jet = piston gone, that explains the lean condition.