Newbie has weird problem!

[Rcman098]

Hello! im new in the forum world so I would like to say sorry for any errors I make while I figure this whole forum thing out. . .

ANYWAY . . I bought my first blaster, a 1994, for $500. Its bored out to 240cc (supposedly) , pro circuit exhaust and muffler and so on . . . It ran ok and defiantly needs a tune up but lately its having a unusual problem :-/

lately when I've been riding no matter what throttle position im in, the engine starts revving up out of no where! it will go good for about a minute then it suddenly takes off. I have also noticed im always having the adjust the idle . .and after it revs up and I shut her down its a HUGE pain to start again X(

it will idle fine and you can sit and rev it all day in the drive way, but when im on it, it becomes hell. I went ahead and ordered a carb kit today just to make sure the carb is 100% even though I took it apart once and it was already pretty clean

Thanks in advance for putting up with my newbieness and for any advice you can spare - Collin I:I

 

[Herpderplol]

AIR LEAK

Trust me, theres no problem you could have that someone here hasnt

Do not run it again until its leak tested. Im sure

Build or buy a leak down tester (Awk08 sells them very reasonably)


Blaaster's post, i dont take credit for it

How To Perform a Leak Down Test – YouTube

Demonstrating a Leak Down Test performed on a Yamaha Blaster – YouTube

 

[Rcman098]

I forgot to mention! the bolts on the head were loose one day and it was running, but it was super loud and I could feel the exhaust hitting my leg. I re tightened the bolts and that was that . .

 

[Herpderplol]

Torqued to 20 ft lbs. ????

You need to leak test your motor ANY time its taken apart, or... has a leak like stated...

You will run dangerously lean with a leak, causing you to need a rebuild after it blows.

 

[Rcman098]

I just tightened them with a socket . . well my friends did . . maybe there night tightened enough or tightened uneven

 

[Herpderplol]

Take them off, TORQUE them to 20 ft lbs.

Then get a leak tester and leak test

Just trying to save you a headache in the future. I:I

 

[Awk08]

if the head or base nuts came loose while running, chances are nothing but new gaskets are going to get it to seal properly again.
the head gasket will at least need annealed to seal again, or preferably a new one
not just retightened and hope it seals.

leakdown test, before and after the new gaskets to insure it is leak free.

 

[Rcman098]

not to sound really new but whats anneal . . .

 

[gb blaster]

Replace that head gasket with a brand new one either cometic or OEM. No paper garbage! Grab a click style torque wrench and torque them to 20 foot pounds.( harbor freight sells a very reasonably priced torque wrench. I wanna say I paid 25 or so for mine?)


I sure hope this isn't true but the first thing I noticed on mine before I had to rebuild was a constant need to readjust the idle. Now with you running under a airleak that's dangerous. I hope u haven't pushed the limits and have caught it in time!

I would recommend a in depth inspection of your cylinder, piston, and rings while your inside there replacing that head gasket.

If nothing else just for piece of mind!

If all checks out just replace the gasket torque down them head bolts and u should be good.


Was that carb jetted properly for that pipe?

 

[Rcman098]

I went ahead and just ordered a new gasket set to go with the carb rebuild. as soon at the engine would rev up I always shut it down so sine the first time the engine revved up till now its probably has 5 minutes of run time

I don't know anything about the carb jetting . . all I know is that the TORS seems to still be installed (not for long) hehe

I got my cousin coming to pick it up and look at it. hes rebuilt a ton of these kind of things so he can fix it

I really appreciate all the Reponses! last thing, Do you think I got a decent price for $500? the fender is broken and the front brakes barely work

 

[gb blaster]

The breaks barley work because there probably the stock pre 03 cable garbage. However if it really is a 240 kit and it's piped I say u did real good!

Also glad u were a smart man and never ran to much till it was fixed.

Replace ur gasket rebuild your carb and report back with the jetting! It's VERRRYYYYY important these little 2 strokes are jetted correctly of you don't wanna shell out a couple hundred on a rebuild.

Also please make sure u leak test after its all sealed up. Idk how many bikes I've seen die since I've been a member because people don't take that advise. It's 20-30 bucks for a tester and takes 20 minutes don't be the guy who regrets it.

 

[terry_j48173]

I would think that its most likely a 40 over bore. Not a bbk. Either way for 500 bucks you cant go wrong.