some advice for carbs?

[zkaoskid]

so recently i went from building tunner cars to playing with quads. in the past 3 months ive aquired 3 blasters. only one was a complete running bike when i got it. we have rebuilt the top end on all three replaced the crank and bearings in one and done what we can to get them running right. up untill last night i thought we had them all running good. bear with me thou the explanations

1st quad: bored .80 over fmf exhaust(dont know which one), kn air filter, boyseen dual stage reeds, 280 main jet and a 35 pilot on stock carb 3rd clip 1 1/2 turns out

2nd quad: bored .30 over everything stock except uni filter 240 main and stock pilot

3rd quad: bored .60over, dg full exhaust, kn air filter, vforce 3 reeds, 270 main 35 pilot 3rd clip 1 1/2 turns out

the 3rd quad we have been having issues with it running weird, we found the intake boot ripped and the cap on the carb kinda stripped so we changed stuff out and got it to run better but not like the other ones, so last night i decided to take the carb off the 2nd quad and put it on the 3rd one took it for a ride and it was a complete monster, ripped the front end up in third gear not trying. now it makes me think is there somethings wrong with the first one, all three carbs have been cleaned a couple times, cant say we have adjusted the float. im just trying to get a better understanding of why this reacted this way.


some enlightenment on the situation would be awesome.

i am a motor addict and have fallen in love with working on and riding these dam lil blasters. once i flip a few more im going to work on building a monster of one fully done up and will hopefully be a regular on here.

 

[Awk08]

IMO, there is no need to run anything but a stock pilot jet on any stock carb, the 32.5 stock pilot is the right size for the air that a stock carb can flow at idle on any blaster motor, even a modded one, anyone who has bumped it up, is covering for other problems

the other settings on them seem close, except the third one.....
a 35 pilot and 270 main jet seem far too large for a dg pipe, which is essentially a stock pipe with the baffles removed
thats why it loved the stock jetted carb

the general consensus on here is .....what pipe being used has the most effect on main jet size, porting being the other major effect

as your experiment last night proved, that dg piped bike loved the stock pilot and 240 main jetted carb, but i'd possibly bump that main to a 250/260

1st bike is jetted close, lose the bigger pilot for a stock 32.5
3rd bike same thing, maybe bump the main to 250/260 and lose that big pilot

and i'd also suggest, since your buying these used, with torn intakes and posssiblty other leaks, you invest in a leakdown tester, to find these airleaks before you fry any pistons, just search on here for
"leakdown tester" theres tons of info on them, and should be in every 2stroke mechanics toolbox
airleaks are our biggest enemy

 

[zkaoskid]

thank you very much exactly what i was looking for. i will look to get my self a leakdown tester this week, im heading out now to go re do the carbs on them before we go riding today. i will post back what the results were. i have a innovate lm2 and if i could log my rpms i wouldnt mind logging my a/f to see what i come up with. any one ever do this? and do you think it would be a bad idea to advance the timing on these?

 

[Awk08]

you would be the first i know of doing a A/F ratio metering, definately keep us posted on that!!!!!!!!!!!!!!!!!!!
and yes, another IMO....advancing the timing 4 degrees is a very popular and cheap upgrade on these, heres the IMO part.....
watch advancing it too far, or in combo with a cut/modded head, which also advances the timing by lowering the plug into the cycle more, hence sparking earlier in the cycle, advancing the timing
search again for the diy on the timing advance, it's on here somewhere, and fairly easy to do

 

[zkaoskid]

cool ill play with the timing mod a lil. i have to finish one of my car projects this week (twin turbo dodge stealth) and then ill see if i can conjure a way to log the rpms on these things. i just need to find a inductive clamp that will work with my lm2 or my laptop. i really want to learn more about the tunning on these creatures and i want to start playing with different carbs. my buddy is picking up a benchtop honeing machine for doing jugs hes out in wilkes barre pa and im trying to get the funds together for a boring bar, i went to school for machining and engine building and other motorsports related stuff. so i wouldn't mind getting serious in to these things. macdizzys site it kinda like my bible to two strokes lol

 

[Awk08]

cool, and the mcdizzy site and way are good starting points.
and the "trailtech" computers for offroad bikes and quads log rpm's, they use a wired washer under the plug to gather the info, dont know if sumthin like that would help ya ?????

 

[best]

My son bought a Blaster and I loved it, so much so I bought my own. Such a simple bike, easy to work on. I had a Raptor 660 but it was waaaayyyy too complicated and heavy, didn't appeal to an old 2-stroker dirtbiker like me.

The "weird washer" is a bimetallic thermocouple to read cylinder head temperature. Like reading exhaust gas temp in a diesel, cylinder head temperature tells you a lot about what is going on inside a 2 stroke cylinder. A minor problem is the reading is delayed a bit, slow to read.

A/F ratio metering doesn't work too well with a 2 stroke because of the lube oil and poor scavenging. It messes up the O2 sensor and there are issues with unburnt air and fuel escaping out the pipe making readings unreliable for what is actually happening inside the cylinder.

I am no expert on Blasters, but have worked on 2 stroke bikes and sleds for many years. Your advice sounds good AWK, Stock or even lean on the pilot and always err on the rich side on the main. Play with the needle for conditions and to get good response. Do plug checks with a new plug to check the main, then err slightly on the rich side to allow for colder/higher conditions. Rich pilot will make a bike feel boggy and dead.

We pushed the timing a couple degrees on my son's, seemed to give some benefit. Most often timing is on the safe side on most vehicles, so a degree or two may help. It is very hard to hear detonation on a 2-stroke, especially with a loud pipe. Much different than hearing it in a car, so be careful. Perhaps best to tune the carb before touching the timing.

One big way we livened up the Blaster was careful attention to piston/head clearance. Stock was over 0.100" (100 thou). We didn't have thick enough solder to measure it! Compression felt soft, bike was hard starting. We dropped that down to 0.065" by means of the base gasket and it really livened up the bike and made it start better. About 0.040" would be the minimum for an air cooled 2 stroke like this, and might make detonation possible.

Oh yes, and gotta adjust the float! It is a tuning tool too. For best results (no lean out at max speed, no overflow on side hills) it has to be right, but a little high or a little low will make the bike rich or lean.

 

[zkaoskid]

yeah ive never really messed with any carbs till the blasters so im a lil iffy on just tweaking it with out measuring but i need to not put it off any more and just do it. i wasnt sure how the mix would effect the reading on the o2 it is of concern. i found some site that had a graph of the 02 readings and roughly where you want them so thats what made me think it was ok to do it. ill still give it a shot i have an extra one for my lm2 if it does ruin one of them. ill have to look in to the trailtech equipment. i know there out there for the four strokes but wasnt sure and havent really looked for the two strokes. well out to go play with the toys now, ill report back later some results. thanks again for all the good info guys.

 

[zkaoskid]

well all is well. i think for the first time i feel the real power of these quads, night and day different, we had a hard time ridding full throttle in our lil pit any more, but im working on a good wheelie now. thank you guys once again for your knowledge and time. ill have some pics and vids loaded in my profile soon and links to vids.

 

[zkaoskid]

oh i ended with stock pilots in all and 270 in the 1st one 240 in the second and 250 in the 3rd, will probley up it a lil on the 3rd after i check the plugs