Hi, I have a 90 blaster that was modded before it bought it. It has a pro circuit expansion pipe and silencer. The piston is 30 over. The carb is all stock except the main jet which is a 270. It also has a stock air box. I'm not familiar with jetting 2 strokes, my only experience is with 4. It has poor low end, very strong mid and flutters past 3/4 throttle. Hard not notice problems in 1st, 2nd and 3rd. From 4th on it really stumbles. The air fuel screw is set at 1 1/4 out. Not sure where to start with this one. Any help would be greatly appreciated.
Correct jetting on a 90 blaster
- Thread starter Reshy55
- Start date
Float is good, I had the carb apart and cleaned it. The reeds are new boyesen power reeds. I haven't checked for air leaks yet. It does leak exhaust gas where the expansion pipe mates to the head, which I feel has a part in this. Also it has a new uni filter with lid on.
If I remember the Pro circuit favours mid/top so do not be concerned if it is not so good down low.
If it is failing up the top above 3/4 throttle when you get onto the main jet, the jet could be too small.
What air filter do you use, pre mix or oil injection?
Any changes which will increase the airflow must be jetted for.
Slip in a main jet #290 and set the idle as per specs and do a WOT plug chop.
Fix that exhaust leak it will cause the engine to run lean, fuel gases are forced back into the cylinder by kinetic energy, if the pipe leaks they cannot be forced back in which results in a dangerous lean mixture!
If it is failing up the top above 3/4 throttle when you get onto the main jet, the jet could be too small.
What air filter do you use, pre mix or oil injection?
Any changes which will increase the airflow must be jetted for.
Slip in a main jet #290 and set the idle as per specs and do a WOT plug chop.
Fix that exhaust leak it will cause the engine to run lean, fuel gases are forced back into the cylinder by kinetic energy, if the pipe leaks they cannot be forced back in which results in a dangerous lean mixture!
i would try to take lid off up the main jet,.....lets put it this way i had my lid on,on my first blaster the wind blew and blew the air right away from snorkel,almost stalled,,,i did not remove the lid but i new that was what happened
your starved for air or fuel ... if you pass a leak test?, compression test?
I have just pi**ed myself! I have now heard all the excuses under the sun and now life is not worth living!
try a 290-300 jet if you have one laying around.
clean/dry air filter?
agee with what blaaster said lmao!
wind would have pushed air into it if anything. you cannot simply "blow wind away" what did you blow it with? carbone dioxide? wind is oxygen
clean/dry air filter?
i would try to take lid off up the main jet,.....lets put it this way i had my lid on,on my first blaster the wind blew and blew the air right away from snorkel,almost stalled,,,i did not remove the lid but i new that was what happened
I have just pi**ed myself! I have now heard all the excuses under the sun and now life is not worth living!
agee with what blaaster said lmao!
wind would have pushed air into it if anything. you cannot simply "blow wind away" what did you blow it with? carbone dioxide? wind is oxygen
I think I need to go back to Technical College, obviously there is a lot of things they forgot to teach me.
Ill work on the exhaust leak first. Everthing on the carb side looks good and like I said filter and reeds are new. The oil injection is blocked off and I have the mix at 32:1 for now till I resolve the problems. This machine feels to have strong compression at the kicker. I will check to be sure. One kick no matter the temp it will fire up and idles like a dream. throttle repsonse at a stand still is very responsive. although it does take quite awhile to throttle down. I have very little experience with plug chopping but I know the basics. Ill start with compression, leaks and then begin the jet process.
That Hanging throttle is ususally a sign of an airleak. There is a thread on how to build a leakdown tester, or PM Awk08, he sells them.
There are numerous plug chopping threads too. Blaaster usually posts a good guide with pics for plug chops, and leak tests.
Those guides are not Moronic thoughts. Just good info from a tried and old mechanic.
Thank you for the help! Ill work on the leaks and see where I stand. Looks like I have some work and learning to do but we all have to start somewhere.
When I am at home and on the mainframe I am able to post files, but I am still trying to come to grips with an iPad Air, which I use when in the field.
Leak test it before you do anything else, if it passes adjust the float, set the idle and WOT plug chop with a #300 main jet.
Be warned strong winds may affect the plug chop, I think not.
Please feel free to start a conversation with me so we do not have to filter silly comments.
Leak test it before you do anything else, if it passes adjust the float, set the idle and WOT plug chop with a #300 main jet.
Be warned strong winds may affect the plug chop, I think not.
Please feel free to start a conversation with me so we do not have to filter silly comments.
. The Blaster is a great machine to learn with. Read up on things on here, and you'll get an even better feel for things.
just ask and us experienced guys will put you on the right track, we will get you running right.
That's a good plan! You'll be glad when its done, and can take pride in knowing you did it.
I sealed up all the air leaks and tried to run it. I couldn't even get the machine to start. So I assume it was tuned with the air leaks. It was leaking bad at the exhaust and intake. Not sure where to start I checked the carb and its at stock settings except the 270 main. I did get a 300 for it but I'm waiting to put it in. Also I checked the float and it was good. Its getting fuel and good spark. I have a larger intake boot and a mikuni 35 off a kdx 200 that I know was working good. I'm wondering if it would work with mine and is it worth trying.
do not fit the 35mm until you figure out how to tune the stock carb.
99% of the time larger carbs have completely worng jets and needle.
start at the bottom and work up.
reeds good ?
float height good ?
try a new spark plug ?
set/adjust airscrew/pilot:
http://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/
the stock 32.5 pilot, airscrew around 1.5 turns out, and needle in the middle position should be good for your mods
99% of the time larger carbs have completely worng jets and needle.
start at the bottom and work up.
reeds good ?
float height good ?
try a new spark plug ?
set/adjust airscrew/pilot:
http://www.blasterforum.com/threads/adjusting-your-airscrew-pilot-jet.51060/
the stock 32.5 pilot, airscrew around 1.5 turns out, and needle in the middle position should be good for your mods
How did you test to see if the engine was airtight, what were the test results?
The #270 jet will not hinder it starting, but do not ride until the #300 is fitted.
Could the reason be that it will not start be that it is flooded from constant kicking.
