Blaster dies after warm up

[Seth Rowe]

Sooo 3rd post here lol. Was going to get rid of this one because of the headaches but made a little progress that's worth trying to salvage it. So I have this blaster. Thought it was a 2000 turns out to be a 88 according to the VIN. Not 100% it is but pretty sure. Anyways. Bought it from the guy, didn't start at the time, took it home pull started it and ran. Always had to pull start it but it would run amazing when it started. Would keep up with my brothers Polaris 250. Had some bogging issues after a week so I figured it was a good time to clean the carb gas etc. Got my kit installed everything and put it back together, started but ran like crap. So I did some changes and it wouldn't fire at all. Sooo after a couple days I put the 250 main that was in it before back in it. Kinda ran but after awhile it'd die. And not start and didn't start for a day or two. So I started going back to the original settings that the previous owner had it at. #250 main, stock pilot jet. Needle clip in 2nd notch. Started to run a little but then would bog out and die like it was loading up. Messed with air screw and air fuel screw. Nothing changed. So I put the original mikuni needle back in (it was slightly bent at the bottom but at that point was trying anything) put the original pilot jet in and the 250 main they had in it. Started up fine no problems. But once it got warm it would bog and neither of the screws would help or worsen it. Kinda out of ideas and ready to sell it or take it to the shop. So close but I'd rather make money on this thing then shovel out more money on someone else fixing it. I know it can't be anything major because it starts up and runs fine till operating temp. I'd definitely appreciate the help. Hoping this thread gets a little more help then my last two
Also the mods on this as far as I know and can see are, air box lid off, tors removed but not off the carb, DG header, stock silencer, and presumably the stock filter. Everything else seems stock.
I'm really hoping to ride this thing more then I have. First four wheeler I've owned and already hooked but problems are getting the best of me

 

[Seth Rowe]

Well Im not having any luck getting any answers on here so I'll try posting this to the general support instead of specific thread. (Don't mean to bombard with multiple posts going to delete the ones that don't pertain anymore) but anyways I was going to get rid of this one because of the headaches but made a little progress that's worth trying to salvage it. So I have this blaster. Thought it was a 2000 turns out to be a 88 according to the VIN. Not 100% it is but pretty sure. Anyways. Bought it from the guy, didn't start at the time, took it home pull started it and ran. Always had to pull start it but it would run amazing when it started. Would keep up with my brothers Polaris 250. Had some bogging issues after a week so I figured it was a good time to clean the carb gas etc. Got my kit installed everything and put it back together, started but ran like crap. So I did some changes and it wouldn't fire at all. Sooo after a couple days I put the 250 main that was in it before back in it. Kinda ran but after awhile it'd die. And not start and didn't start for a day or two. So I started going back to the original settings that the previous owner had it at. #250 main, stock pilot jet. Needle clip in 2nd notch. Started to run a little but then would bog out and die like it was loading up. Messed with air screw and air fuel screw. Nothing changed. So I put the original mikuni needle back in (it was slightly bent at the bottom but at that point was trying anything) put the original pilot jet in and the 250 main they had in it. Started up fine no problems. But once it got warm it would bog and neither of the screws would help or worsen it. I've read probably 100 threads trying to help me but nada. I wouldn't think it be compression because another post someone said if it had low compression it wouldn't run at all??? I pulled the plug after a somewhat WOT run and it was a dark grey but not wet and no signs of any white meaning lean. My dad knows a lot about engines and said the plug was alright. It wasn't the best but it wasn't lean.

Kinda out of ideas and ready to sell it or take it to the shop. So close but I'd rather make money on this thing then shovel out more money on someone else fixing it. I know it can't be anything major because it starts up and runs fine till operating temp. I'd definitely appreciate the help. Hoping this thread gets a little more help then my last ones.
Also the mods on this as far as I know and can see are, air box lid off, tors removed but not off the carb, DG header, stock silencer, and presumably the stock filter. Everything else seems stock.
I'm really hoping to ride this thing more then I have. First four wheeler I've owned and already hooked but problems are getting the best of me.

 

[TRider06]

There may be an electrical problem. You said the tors was removed, I would double check the wiring and the coil. Sometimes when coils go bad and get hot they can stop working right. (Had that happen on a
Couple of small engines I worked on). Also regarding your carburetor, I would take it 100% apart even the “emulsion tube” part that the main jet screws into, clean out everything. And assemble it the way it was originally. Stock pilot jet, 250 main, and I would set the needle clip in the middle position. Set your air screw 1.5 turns out to start. Also, are you still running the oil pump?? If your oil pump is removed, make sure the small brass nipple on the right side of the carb is blocked off. So no air will enter. If your oil pump is removed that is probably why there is a 250 main jet, to run the 32:1 mix. Hope this helps.

 

[Noxtol]

How is the compression? from what you're describing it sounds like a compression issue espessially since it dies after warming up.

 

[Seth Rowe]

Well i checked it before and it was around 105 (low I know) yesterday I checked it. It was barely 60 psi but it held steady. My dad suggested putting some oil down the plug hole to narrow some answers down to piston rings or at least one of the problems. Which it ended up rising to 90 psi. So after that I just pulled the head off and now I've got the top end opened up. It's got a hot rod crank and rod in it. I'm presuming it's trenched or is that only for the stroker rod? Stock piston head from the looks of it as well. I will upload pics. Cylinder wall looks really good and my dad could see a bend in the ring when he set it in the cylinder, guessing that's where I'm losing the last 50 or so psi of compression. Also what should compression range from?I micrometered the cylinder. It is 2.612. So what's your guys opinion?? Also will test the coil tonight. Am I checking the ohm's? And what is passing numbers for coil. My dad also thought it has been re-sleeved.? Guessing they maxed out the bore and had to go back stock. Not sure though. Saying that cause there's a 1/8 in sleeve in the cylinder that's a brownish color and then the cylinder. I'll post a pic of that as well.

 

[Seth Rowe]

Don't mind the paint. Bought it cheap. Lolol. If motor is worth saving I'm going to redo it all. Don't want to throw money away. Which I know will happen at some point on these things. I also thought about changing the piston head. Should I keep the rod and crank or just redo it??