2000 Blaster question

[youwish0411]

Hey guys. New to this forum, however not new to yamaha or two strokes. I bought a 2000 blaster last summer. I put about 5 hours on it and blew it up. Here's my question. When I tore the top end off, the rings were fused to the piston and not one part of them were missing, the cylinder and piston were scratched something horrible and had flakes of metal fused to both the cylinder and piston. I will post pictures of the piston when i get home. Have any of you ever seen this happen? Everythung from the top end was accounted for. Ie, wrist pin, circlips, bearing. The top of the piston was flawless as was the head. Any ideas?

I did just buy a new entire top end for knowing it's going to need it. Really don't want to have to crack the crank if I don't need to... I realize this is probably wishful thinking but ya never know.

Willing to listen to any ideas. Thanks!

 

[Awk08]

welcome to BF.

sounds like shrapnel from a bottom end bearing made it's way into the top end.
check for up/down play of the connecting rod, there should be very little to none, and side to side play should be around .028
for main bearings, check for up/down play of the crank ends on both sides and feel for rough spots when rotating.

downloading the service manual will help...
http://www.blasterforum.com/threads...ervice-and-owner-manuals-free-download.17325/

 

[youwish0411]

Ok. Pictures to follow. Hopefully they will help.

Thanks awk for the reply. That's what I'm thinking (something from the bottom end) but then why is the top of the piston and head not gouged at all?

 

[youwish0411]

Ok. Here are some pictures. Don't mind the gouges by the wrist pin opening... that's from me beating on it... oops...

 

[Awk08]

that could just be seized from running too lean or an airleak ?
but you have the topend off so it'd still pay to check the bottom end.

what were you doing when it fried ?
temps, jetting, mods ?

 

[youwish0411]

I was just going for a ride. Nothing rough. As a matter of fact I was on a gravel road. to be honest, I don't know about mods. The guy I bought it from said he bored it over .050? Never heard of that measurement but I'm by no means an expert. It has full fmf exhaust, I think it's got a no-toil air filter (It's been a while since I've actually paid the bike any attention). Oil deletion on it so pre mix gas at 32:1. I was running a step cooler plug at a br9es.

The temp was mid 70s I'd say with an elevation of around 800. Jetting.... I can't quote you on that... I wanna say stage one kit but he never gave me numbers for each jet. Haven't torn the carb apart yet to be sure. I could do that tomorrow though.

 

[Awk08]

holding it wide open or at a steady throttle position for miles down the road is a recipe for disaster on these little air cooled engines, unless jetted extra rich.

yes, check what main jet is in the carb, and clip position of the needle clip, and report back

 

[youwish0411]

I know that about the throttle. I was pretty anal about the throttle actually. My fiance was riding a four stroke with me and kept gutting mad because I wouldn't stay at a constant speed. So I would like to say that THAT wasn't the issue.... but really... who knows...

I will. I will get those numbers and get back to you! Thanks you for your input! I really appreciate it awk!

 

[Blaster8821]

I had the same thing happen from an air leak. It was running fine then just died and had no compression. Opened it up that night and rings had seized to the piston.

 

[tbrooks]

First things on a new to you 2 stroke, leaktest, compression test, and check the jetting, oil and filter. Jet kits are often completely useless, and the numbers on them won't mean much to us, the only way to ensure correct jetting is a plug chop. My guess is it was not properly jetted or had an airleak which caused your destruction. Since it is new to you and you have some damage there, it would pay to split the cases and put new bearings and seals, and check everything out while your in there. Why did you buy a new top end? If thats all it has been bored, than all it needs is a bore and piston. Also no need to change plug heat range, these engines were designed to run a br8es or b8es, and so that is what you should stick with.

 

[Blaaster]

To me the pics suggest that the piston has suffered lubrication loss due to holding the throttle near or wide open for a long period.

At large throttle openings on small high revving engines the oil does not have time to come out of suspension and pool in the crankcase to be thrown around to bathe the moving piston.

There seems no sign of detonation or heat affected area on the piston crown, but close inspection of the underside of the crown may determine if the piston was overheated, it will show as baked on burnt oil.

It is perfectly ok to hold any 2 stroke wide open for long periods but a 32:1 oil ratio will not supply enough lubrication for an engine of 200ccs. The higher the revs and the smaller the engine the more oil you have to throw at it.

 

[dirtysquared]

I saw you say you bought an entire new top end for it...was it new, or did you just get the cylinder bored to the next oversize? Reason I ask is some members have bought the ebay kits, and had to do alot of work to them to make them acceptable. They have had lack of chamfering of ports, etc etc. Just something to keep your eyes open to. I'd hate to see you go through all the trouble, only to snag a ring on a port.

Lots of good info here and good members that enjoy helping each other out. Welcome to the Forum

 

[jus_me]

That sux because it looks like it "was" a newer piston. Like the previous owner stated he did a new top end with a bore. The question is if he measured everything correctly and actually bored and not just honed a worn out cyl and threw in the next size piston is any ones guess. No time better than the present to do it over and correctly. You are in the right place for any and all info you will need on these fun little quads. Also look into a leak down tester, you are going to need one owning a 2 stroke.

Stick around long enough and you will be the one yelling at the fiancée to catch up ..

 

[youwish0411]

You guys are awesome! Some great info on here! I bought a new top end just to buy it I guess. When I tear things apart, I like new stuff to put back on it. I just got the top end today actually and it does need chamfering that's for sure. There's a little small engine shop who I've dealt with previously in town and I may just bring the top end to him. Those edges are pretty sharp.

When I bought it, the guy said it was a new piston and the cylinder was bored out. It looks like the old one was sleeved, but even the guy at a yamaha dealer said he couldn't be sure. It was done pretty piss poor and that's easy to see.

Right after it blew up, I took it to a very veteran mechanic and asked him his opinion on it and he said he couldn't tell what happened. He did say he could promise me that it was NOT from heat.

I took the carb apart today and the main jet is a 230 jet if that helps out at all.

 

[youwish0411]

Here is another question for you guys. If (or when) I open the bottom end up, can I use the same crank and rod provided they aren't broke? Or would you guys suggest I get a whole new bottom end too?

Thanks!

 

[tbrooks]

230 is way lean for that fmf, especially in winter. Yes you can use the same as long as it checks out, in fact I think most would recommend it. If there is a problem with the crank they can be rebuilt as well

 

[youwish0411]

Well I only ride in spring/summer/fall. I'm in northern minnesota so it's waaaay too cold to ride in the winter.

Good to know about the crank/rod. That saves a few bucks.

I was doing some research... I found that a 230 main jet is stock? If that's true, with an oversized piston, full fmf exhaust and after market air filter, that would be way too lean correct? If that is the case, I think I can see how the thing blew up...

 

[Awk08]

I was doing some research... I found that a 230 main jet is stock? If that's true, with an oversized piston, full fmf exhaust and after market air filter, that would be way too lean correct? If that is the case, I think I can see how the thing blew up...

that /\
full FMF's usually require between a 270-300 main jet depending on airbox/filter mods, altitude and temps.

 

[youwish0411]

Ugh... I ended up buying this guy's problem.... ok. So now when it gets fixed, with a stock size piston in it again but fmf exhaust, that is the jet I will need. And to figure it out, plug chop it. What about a pilot jet? I'm assuming the idiot I bought it from left that the same too... so any ideas on the pilot jet then?

 

[Awk08]

Ugh... I ended up buying this guy's problem.... ok. So now when it gets fixed, with a stock size piston in it again but fmf exhaust, that is the jet I will need. And to figure it out, plug chop it. What about a pilot jet? I'm assuming the idiot I bought it from left that the same too... so any ideas on the pilot jet then?

I've run the stock carb on many states of tune and different pipes, the stock 32.5 pilot has worked for all of them.
it gets adjusted richer/leaner with the airscrew...
http://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/

I'd buy 270, 290 & 300 mains, start large and plug chop down.