Fresh rebuild with minor mods, can’t get it to run right

MN Squatch

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Jun 4, 2019
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So I rebuilt my 02 blaster this winter after I fried it a couple weeks after buying it last summer. When I did the fresh rebuild (jug, piston, rings, gaskets) I added dual stage boyesen reeds, ported and polished the jug, and removed the box air filter altogether and put a cone filter right on the carb. I quit using the oil injection because I suspect it may have had something to do with the top end blowing. Currently running 40:1. Let me add that I’m a total rookie at all of this, it’s my first 2 stroke, and really my only mechanical inclination comes from being a machinist by trade. I had the engine running relatively good aside from the fact that it would start bogging down about 10 minutes after riding. I was running the stock 230 main jet with the needle and float clipped on the very top groove. After reading some threads I decided to try moving the clip back to the middle and running a 270 main jet. This made it bog down much more. I’ve heard of plug chopping but don’t really know anything about it. Does anyone have any recommendations on what to do next? I’d like to be able to get the jetting dialed in without having to guess and check without really having a clue what I’m doing.

All input welcome
 
So I rebuilt my 02 blaster this winter after I fried it a couple weeks after buying it last summer. When I did the fresh rebuild (jug, piston, rings, gaskets) I added dual stage boyesen reeds, ported and polished the jug, and removed the box air filter altogether and put a cone filter right on the carb. I quit using the oil injection because I suspect it may have had something to do with the top end blowing. Currently running 40:1. Let me add that I’m a total rookie at all of this, it’s my first 2 stroke, and really my only mechanical inclination comes from being a machinist by trade. I had the engine running relatively good aside from the fact that it would start bogging down about 10 minutes after riding. I was running the stock 230 main jet with the needle and float clipped on the very top groove. After reading some threads I decided to try moving the clip back to the middle and running a 270 main jet. This made it bog down much more. I’ve heard of plug chopping but don’t really know anything about it. Does anyone have any recommendations on what to do next? I’d like to be able to get the jetting dialed in without having to guess and check without really having a clue what I’m doing.

All input welcome

(edit)
Made some adjustments to the idle and air screws on the carb and it seemed to make a huge difference. Running much better now.
 
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(edit)
Made some adjustments to the idle and air screws on the carb and it seemed to make a huge difference. Running much better now.
Glad to hear its better. But is it right? You can find alot of power in these if tuned properly.Most are premixing at 32:1 on these air cooled blasters.
Some have had problems running the air cleaner right of carb. Maybe air turbulence?
Unless your. Riding on the street or some clean environment.no water? OrDusty area's. Then an exposed filter element may work. Otherwise using your stock airbox with lid off or holes drilled in lid is your best option besides an aftermarket air box.
There are also some good articles on carb tuning on the forum.search carb tuning.
It will explain the proper procedure to tune and jet the carb. Also plug chops verify that your jetting is correct. Last thing you want is to run lean. It will fry your new rebuild.
A 2t leakdown test after a rebuild is also a good idea.
 
these bikes like 32:1 mix and all jetting info on here is based on that.
make sure you remove the rubber hose from the pump to carb and cap off that brass oil injection port on the carb, 1/8" rubber vacuum cap works well

check set float height
airscrew at 1.5 turns out to start, tune with 1/4 turns to find highest idle, allowing 10-15 seconds between each turn for the engine to react to the new air/fuel ratio
clip on the middle slot of the stock needle
270 is probably too rich for your mods without an aftermarket pipe, probably add 1 size over the 230 main jet for the oil injection delete and 1 or 2 more for the cone filter, putting you in the 250/260 range to start
plug chop to confirm: https://www.blasterforum.com/threads/how-to-plug-chop.53237/
and adjust accordingly

cone filters directly on the carb are known to cause jetting nightmares for anything but wide open throttle drag bikes
there's just too much turbulence from having it directly on the carb, hook the stock airbox and boot back up, or add a 4-6 inch pvc pipe between carb and filter to allow the air time to straighten out before going over the jets
 
I’m gonna do the float height tomorrow, I’ve never checked it. I put the 230 main jet back in for now, ordered a 220, 240, And 250 as well as a 30 and a 35 pilot jet. I’ll have to try the pvc on the air filter because my wife was sick of the clutter and made me throw out a bunch of the atv parts that were just laying around (the air box was one of them).

I was also wondering about the big idle screw under the seat? I think it’s on the TORS? I hadn’t even known that existed until tonight and I was messing with it and I wasn’t sure where it’s supposed to be set.

It’s not running perfectly yet, I was messing with the air adjustment a bunch while I was buzzing around on it rather than while it was sitting at an idle and I got it to run best somewhere around 2.5 turns. Really don’t know if it matters though since I haven’t checked the needle height yet and it could change once I do that.

I’ll keep tinkering away and maybe one of these days I’ll actually feel like I know what the hell I’m doing!

Thanks for the input!
 
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I’m gonna do the float height tomorrow, I’ve never checked it. I put the 230 main jet back in for now, ordered a 220, 240, And 250 as well as a 30 and a 35 pilot jet. I’ll have to try the pvc on the air filter because my wife was sick of the clutter and made me throw out a bunch of the atv parts that were just laying around (the air box was one of them).

I was also wondering about the big idle screw under the seat? I think it’s on the TORS? I hadn’t even known that existed until tonight and I was messing with it and I wasn’t sure where it’s supposed to be set.

It’s not running perfectly yet, I was messing with the air adjustment a bunch while I was buzzing around on it rather than while it was sitting at an idle and I got it to run best somewhere around 2.5 turns. Really don’t know if it matters though since I haven’t checked the needle height yet and it could change once I do that.

I’ll keep tinkering away and maybe one of these days I’ll actually feel like I know what the hell I’m doing!

Thanks for the input!
You will get it.float height is the first thing to check when jetting. If it is off it will affect all circuits
 
The big screw on top of the tors is the idle screw, if it doesn't change the idle speed they have been known to mess up, it's cable driven inside the tors box, and not repairable as far as I know, hence why most of us switch to the tors replacement cap and cable and add an idle screw to the side of the carb. search ebay, Vito's and Motion Pro both make them if needed

2.5 turns out is within acceptable limit for the airscrew, any further could suggest a larger pilot is needed, but I've never needed one on stock to ported and piped machines, same with the needle, stock needle on middle clip position has worked on them all.

start at the bottom and work up, get one circuit right before moving on to the next
float height
pilot/airscrew
needle
and plug chops for the main jet last
 
So I’ve got it running really well. Still have the stock main jet and pilot jet in there and I added the pvc to the air filter to give the air some time to straighten out. I tried running my needle clip in the middle groove, then went up one to make it richer and it ran even worse, so I went the extreme opposite to the top groove to see if I was making it better or worse and it ran unbelievably well. It was running almost too well and my idle was super high, even after adjusting my idle screw. So I backed the clip down one groove because I’m nervous about running it too lean and having it blow up on me. It isn’t quite as zippy and responsive at this setting but it seems like the safe thing to do. I took it out for a 15 minute ride tonight where I was in 6th gear 75% of the time because it’s nice flat gravel roads mostly. I would occasionally give it full throttle when I was on straightaways but then back off and just give it half throttle so it wasn’t redlining the entire time I was on my ride. My little red light by the handlebars came on by the time I got home, which I assume is a temperature warning? It would really be a bummer if I can’t drive this thing for more than 15 minutes at a time.


What’s normal for other people? Can you take your blaster out and ride it nonstop for hours at a time without worrying too much about it overheating? Is there something I can do to prevent engine temp from getting too hot? Is it just going to be a matter of time before my fresh rebuild is broken in and this won’t happen as much?
 
The red light on the dash is the low oil warning light for the oil injection tank, if you're still using the injection, it's time to add oil
but these engines don't do well on roads at long 3/4 to full throttle runs, unless jetted rich for those conditions.
these were designed for, and shine in the woods and trails
 
So my oil tank is full... what could be causing the light to come on then? And what do you suggest then if I would like to do more long distance cruising on it? I have a 3 mile ride any direction to get any trails. Should I bump up my main jet a little bit since I’ll be using half to 3/4 throttle most of the time to get to and from my destinations?
 
check the wiring to the oil tank to see why the lights on, bad float switch in the tank ?

1/2 to 3/4 throttle is all on the needle jetting,
3/4 to full throttle is main jetting
if you drop the clip to raise the needle and richen that circuit for long road riding, I doubt it will run good in the trails ?
I'd be at least giving it some full throttle every now and then to feed it all the fuel/oil you can during those long runs
 
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So I’ve been told that the light can come on when your oil temp gets too high also. I’ll probably leave the needle right where it is because it really didn’t run very good with it in the middle position. I’ll just have to keep an eye on things.
 
So I’ve been told that the light can come on when your oil temp gets too high also

Absolutely not, that's a 4 stroke guy telling you that, our engines hove no oil in them besides the trans fluid and it is not monitored for level or temp.
the light is connected to a float valve in the injection oil tank only, how would that get hot ?
keep your tank full and disregard the light