Hello, My name is Dane.
I recently bought a 2000 yamaha Blaster 200cc.
It has very little compression.( It wont start)
Sometimes when I kick it to start it, The piston catches in the cylinder and gets stuck. I took off the top cylinder head and the piston crown has a few tiny dings on it where something has either fell down thru the sparkplug hole or some other metal has came up from the lower end.
The cylinder walls look really good though with no abrasions and is still really smooth.
I am thinking that it could be that my rings are shot and cracked or broken and this is causing the piston to catch.
I would appreciate any input.
Is my thinking correct about the rings?
I will take the lower head off today and post pictures.(If I can find out how to post pictures.)
Also, I dont believe its ever been bored out for the piston only has a marking on top of Ex and a arrow pointing to the exhaust and just opposite of that the numbers 8592. Which I would think is stock.
Thanks for any reply, Dane

 

Hi Dane, it could be a number of things, first look at the spark plug and be sure there is no damage to it first. Second do a compression test. If you have a compression gauge great, get someone to kick the engine over while you hold you thumb or finger over the spark plug hole. It should blow your finger off with good force. If not. Get ready to rebuild the top end. If the cylinder walls are not all scratched up I doubt you have broken rings. Hope this helps you.

 

Sounds legit to me.

If you have the head off already just pull the jug. If you have very little compression sounds like the rings and piston are junk.

Let us know what you find out.

 

I took off the top head and lower cylinder, The piston was actually broken-A piece was actually missing and no where to be found-There was no rings either-I guess the guy I bought it off of lied about the whole engine. Heck the ad said just need front and rear brake lines-The back brake caliper was missing all the innards!!
So I took the head to be bored and order piston, rings, bearings, and gaskets for it.(All the top end Stuff) What a nightmare, I never figured to put 300 more into it- But I only paid 300 for it so all in all I will have 6 or 7 into it total.
I am concerned now with the little bit of play I have on the piston rod where it connects to the camshaft, There is a little play up and down as well as sideways- I sure hope that this doesnt need replaced because I just cant afford to do it, Plus thats a whole lot of work. The tools alone to do the job are up there.
It doesnt have a excess amount of play -maybe a 1/16 inch up and down and sideways. I hope that thats within specs?
If it isnt in specs and if I dont replace it I am wondering if this will be ok.?? I am worried about piston slapping though if it isnt within specs??
Any ideas?
I am also looking for a rear brake caliper unit. I wonder if a rebuild kit will have all that I need to fix it-Its missing all the innards.
I guess while I have it tore down I will clean it all up and Paint it too.
Thanks for the input,
Dane

 

Well, wow, that's not good. A 1/16 of in inch is a LOT of play up and down. For side play it is fine.

One good thing you have going for you is a two stroke is a lot more forgiving than a 4 stroke as far as rebuilding goes.

I have had many two strokes that were loose as a goose and still ran pretty good. Not so with a 4 stroke.

Anyway I would just put it together and see how it sounds. If it runs good then go have fun. If it knocks then save up for a crank job.

Let us know how it goes.

 

I just got it bored and new piston/ rings and gaskets and it started on the 2nd kick, So i let it idle for 15 minutes, shut it down and retorqued the heads, I did this three times and all was going well. But then it started reving up by itself so I adjusted the air/gas intake in by 1/8th turn and it quit on me and I have not been able to restart it. It seems like it is too lean on gas, but no matter how i adjust it it wont start. It backfires sometimes if I prime the intake with starting fluid. It has compression and it has spark. It has the old tors system on it I think, but its not attached to the carburetor, It is conected to the throttle and that leads to under the front cover and it is conected there as well. I am wondering if it could be the tors unit from keeping it from starting. I noticed that it had a minute air leak where the carb is connected and that may have caused it to run lean during its breakin and I just hope that It wouldnt of burned up my rings that quick? It ran for around 10 minutes 3 times before it quit on me. When it quit it didnt make any weird noises so I wouldnt think it would be my rings, because it has enough compression to blow my finger off the sparkplug hole. I am really at a loss. Should I take the top head off and look at the piston and rings? I will have to get a new head gasket if i do wont I?
Any assistance would be helpful. I am at a loss.
Dane

 

Yes 10 minutes of lean running on a fresh build could have just bought you another top end. I would pull the head and check the cylinder walls before I did anything else. Intake leaks are not good. Fix it. And yes unplug the tors from under the front cowling. Really hope your engine is ok.

 

There is no need to take the head off if you have good compression. You might want to buy or borrow a compression gauge to get a number.

The only way an engine can rev up by itself is if you have an air leak. That is the only way. You have an airleak somewhere and it might not even be the one you are talking about.

It could be anywhere. Carb boot, crank seal; anywhere. You need to fix ALL airleaks before you do anything else.

You said it backfires so you have spark.

Where would I go from here? I would check to see if you did not break a key and the timing slipped. If this is ok then I would see if you getting gas.

Let us know what you find.

 

I tore it back down and it needs a new crankshaft, bearings and seals.
Everything is wobbly down there!! Sounds like a bunch of marbles roling around!! The guy really took me on this one!!
So i am buying a new crankshaft for it.
I was thinking of a WISECO ENGINE CRANK ASSEMBLY because its already pressed and ready to install and it comes with all the bearings,gaskets and seals. Or a Hot rod crank, if they come prepressed.
What would you suggest on the Crank?
I cant afford to put more than 220 dollars more into this thing. I plan on reselling it after I get it running. Ive already got 660 dollars invested in it total! As it is Ill barely brake even if that!!
Then also I will probally have to buy a crankshaft remover/installer tool because I imagine that it will be hell if not impossible to get the old crank out and the new one seated in correctly.
Any suggestions on that tool?
Thanks Dane

 

Well that sucks.
Wisco makes good parts. I don't know about the Blaster though.
I also can't recomend a puller because I have never had a Blaster apart.

Let us know how it works out for you.