Blaster idles good,crack throttle and revs but sputters some till wot

[procharger]

Hello,

I like this forum, very good info on here. I am working on a friends blaster and have run into a problem. He brought it to me and said it would bog bad at the hit, but run better towards top end. It sat all winter and when I got it,I put a fresh b8es plug, fresh gas, drained oil from tank, he was afraid that someone put the wrong oil in tank. Replaced it with Yamalube. It would only run with choke out and then ran bad. Took carb off and cleaned completely. Pilot jet was closed off, choke circuit dirty and main was clear.32.5 pilot jet. main is original. air filter clean. Put carb back on, found 1 tors wire broken at butt connector, repaired. Adj air /mix screw to 1 1/2 turns out .Filled bowl,filled oil line and started. Runs and idles good now. Bogs and the initial crack of throttle, then cleans out till around 3/4 throttle, Then boggs and finally revvs up to wot. When you ride it, as long as rpms kept up, runs great and has good power. Return to idle and runs smooth and never cuts out. I have also sprayed with wd40 to ck for air leaks. Seems ok and does not revv up. could the tors cause this? the bike ran great for 2 yrs till last fall and this started. I think its a 2002 model Iits has black fenders and red/blk tank and blk seat. Only mods are a fmf fatty and silencer, k/n air filter. almost forgot, took lid off air box and revvs quicker and has slighter less bog off the hit, but goes to wot throttle quickly.am I missing something? does not smoke like a ring is stuck or anything. .starting to get frustrated .any thoughts..thanks..Eddie

 

[Herpderplol]

So you are saying the jet is original with those mods??? I can see why its running bad, although normally a lean mixture causes high idle and a little more power while wrecking the engine.

I suggest a #290 or #300 main jet
Air screw out 1.5 turns
Get a leak down tester and check for leaks, spraying it may for, but this way is for sure

 

[Wifesblaster]

Well here are my thoughts. First and most importantly if that bike has an FMF exhaust on it with a stock main jet it will fry the piston. You will need a 270, 280, 290, or 300 main jet with that pipe. You will have to plug chop to confirm. Could be an air leak too. You need to pm member AWK and buy a leak tester. You can build one, but not worth the time and hassle IMO. Next thing is disconnect the TORS. You don't need it. You said you drained the oil tank. I have deleted mine and I'm not real familiar with them, but I think you have to bleed it. You also have to use an oil that is suitable for oil injection.

 

[JBRoc01blaster]

All good advice above, that bog/hesitation when you first hit the gas definitely screams lean mixture ! All the other jets should be fine but you absolutely need a bigger main ... Start with a 300 or maybe even a 310 to be safe, plug chop to confirm and go down 1 size at a time if needed !

 

[procharger]

So you are saying the jet is original with those mods??? I can see why its running bad, although normally a lean mixture causes high idle and a little more power while wrecking the engine.

I suggest a #290 or #300 main jet
Air screw out 1.5 turns
Get a leak down tester and check for leaks, spraying it may for, but this way is for sure

He told me that the main is original. His daughter rode this bike like this for 2 years. it idles good,but i noticed after I posted in here that it seems like i adjusted the idle thru the tors(since there is no idle screw)and it set to where it is now,but will not idle any higher,no matter how many tyrns you move it in..Can you get a kit of different jets. if so,I will get some and try. He really wants to try and keep it safe for his daughter.I suggested a throttle swap out and eliminate the tors block completly,but he would like to keep it if can. If you do like I have seen in this fourm and unplug the box,and twist the wires at the carb together,how do you change the idle?

 

[procharger]

I will have to pm him, my buddy said he might go ahead and put a piston and rings in it since its completly stock. Then all the gaskets will be new

 

[Blaaster]

An initial bog can be caused by a number of things.

Air leak.
Float level.
Incorrect idle adjustment.
Incorrect needle setting.
Poor compression.

If that motor has been running a FMF with a #230 main jet for 2 years, I would be suspecting a very sad looking piston.

Forget about a jet kit they seldom contain any jet you can use, buy them individually.

 

[Herpderplol]

He told me that the main is original. His daughter rode this bike like this for 2 years.

Can you get a kit of different jets. if so,I will get some and try.

If you do like I have seen in this fourm and unplug the box,and twist the wires at the carb together,how do you change the idle?

You will probably need to rebuild the top end if it ran that way for two years....

There is a website for jets, i forgot it right now, but blaaster posted it about 2 days ago

You also unplug the wires coming out of the throttle and twist them together.

If the TORs block is on there, use the screw to adjust the idle

If the TORs should be removed, you need to install an idle screw on the left side of the carb.

 

[JBRoc01blaster]

Jetsrus.com, or some atv shops/dealers carry main jets ... I got mine at a local dealer/shop for $3.50 and they were genuine mikuni jets !

 

[procharger]

Thanks for all the info.I ordered a piston and rings,gaskets and jets today. We will see how it turns out and let yall know

 

[Blaaster]

Thanks for all the info.I ordered a piston and rings,gaskets and jets today. We will see how it turns out and let yall know

I presume that you measured the size of the bore and checked to see if it was in within specs.

 

[procharger]

I held off ordering parts. I told him I wanted to do a comp test before it was torn down. Weird thing,I pulled the plug and ckd the compression.When I pulled the plug,it was not fouled,and had a bit of oil on the tip,but was not soaked.seemed weird.anyway I ckd the comp and it was 90psi with throttle wide open.according to what I have read that's low.dont know if too low,but lower than where it should be.i ran it for a few and ran like crap till got pretty warm and started to run a bit better.anyway what is the bore size supposed to be..i will year it down this week and measure if cyl shows no sign of damage.if scored will get it machined..would it be safe to say that when this is fresh I could bump the main to 300 as a good starting point or is that too much.thanks

 

[dirtysquared]

good thing you held off ordering parts, Measure the cylinder. If it were me , Id send it out to be bored, honed, finished and have them match the piston to the new bore size. Get it back install, leakdown test. re-jet and plug chop to perfection. There is a few great threads about jetting on here.

 

[procharger]

Well.i tore this apart today. Found the exh side of the piston missing below the wrist pin. Looks like it broke from side to side. Problem is,I cannot find the broken pieces.the bottom of the jug is marred up a little but did not get into the sidewalls of the cylinder..could it have burnt up from being lean and went out of the exhaust? I looked in the crankcase.drained oil.it never made any noise like something was in crankcase..the safe bet would be to tear the entire thing apart and go through it I guess..what do ya think???

 

[Blaaster]

The only thing to do is to split the cases and find out if some piston bits are lurking in there.