vmax carbs

[SRXfromHELL]

Tyler
how are you making out with the 38s on your 81srx ? I have the same carbs for mine
Kevin

[tyler440]

i havent really worked on it much in the last week or so... last time i messed with it i realized that the vent tubes on the top of the carbs fell off and were in the belly pan... dont know how i didnt notice that or how long they have been like that!... i have 2 shims in my clutch now but i havent started it since i did that... right now the oil pump is off because i suspected it to be faulty(too much oil)... but the guys on totally yamaha seemed to think it wasnt.... is still have my doubts(sorry if your the one that told me it was fine)... maybe ill take a picture of the amount of smoke this thing is making and then post it!... ill definatly keep you posted and you better believe that when i do get it figured out ill have an article in the article index... untill then if you wanna come polish my running boards your more than welcome

[SRXfromHELL]

LOL no thanks I think I'm polished out for now . the running board are easy , smooth and flat . try the crank cases or the jugs they are the hardest . as for your oil pump no clue as my autolube is gone I would assume it would smoke pretty bad with the 540 pump and premix . it could also depend on what brand of oil your using . some just smoke more than others amsoil will produce very little smoke where pennsoil will control the bugs for months .
my opinion would be the pump is probly working but may be out of calibration , did you set the pump stroke to spec ? my srx manual shows 17:1 at wfo whatever WFO is assuming it wide open thottle the extra amount of oil from the 540 pump over the 440 pump plus the premix would be alot of oil ! but as I understand these things need a lot of oil . only time will tell . I'm going with 20-25:1 premix and see what happens. would love to put my 44s back on she really ran with them on but 3 burn downs last year hurt
was running 50:1 might not have been the carbs but I have the 38s and the airbox now so I'll try them .maybe put the 44s back on if it stays together with th richer mix ratio .
I tried the 38s late last year and were pretty boggy but it was in the high 40s , I'm pretty sure I have the same jetting that you have right now the numbers sound right so let me know how your doing tunning them
Kevin

[tyler440]

i started this post at 11:30 and finished it 12:15.... im tired... so please bear with all of my typos, cause im not proofing this im going to bed

first off i put the stock 81 oil pump back on, with a vmax cable that runs to the thumb throttle(duh) got that back to gether after dropping the one allen bolt for the pump about 5 times then i put the oil tank back on, and replace the vent tubes on top of the carbs., next held the thumb throttle open with my trusty rubber band(the only way it will start, that i have found) no choke, just pull it about 5 times and it with each pull it trys to run more and more... finially it starts and is real boggy but eventually revs up. by this time you best have the rubber band off or else the motor sounds like it is going to scatter even tho it is only turning around 6000 (guess thats the norm?).. i revved it off and on untill it got warm and then i started to do MY best assement of it... clutch engages right around 5200 with the purple spring and two shims (thats a plus), it seems to WANT to idle around 3500 or so, althought it wont idle for long with out shutting off.... when i hammer on it from idle it snaps for about 250 rpm and then bogs until right about them time the clutch engages from there it seems fine up until 7000 (thats as fast as i have got it to date)(the motor only has like 7 miles on it) all the while im watching all of the fuel lines suck air ocassionally, must be running out of gas i think.... i continue to play with the throttle with no real improvement from the last 5 setups i had.... so i got to grab a screw driver to turn the air screw..... it stalls.... i pull it three times and it starts just like it did when it was cold... reall boogy for ahile(im talking 15 secs) and then lookout it starts reving fast! (not really faster than any other sled ive ever rode but fast) ne ways i get the damn thing started and turn the air screws in about 1/4 turn (this should make them, form what i recall, 1/2 out) didnt seem to change ne thing.... so then i continue to think as keep it running.... this is about the time i watch the fuel lines go from some air to nothing but air..... and about 10 secs after than it shut off... outta gas.... si i fill the thing with about 4 gallons of raw gas.... now mind you there appeared to me 1/2 gallon of mixed that it couldnt pick up... so technically my gas still has a small amount of oil in it... (im not about to try to guess the ration as it is midnight, and im tired).... ~5 pulls and it starts up as usual..... now im expecting to see less smoke....... i wait and wait and wait and wait... i must have held that thing at 4000 for 2 mins and still the smoke just poured out. hmmmm, i think, thats dumb.... i think this is about the time i see some fuild that looks a little thin near the exaust.... upon further inspection i realize that the belly pan has a wonderful fuel/oil mixure puddling in it.... yikes!! i dont wanna catch this thing on fire before it even sees snow!.... so i starting shinning around with my light.... turns out i find fuel "spritzing" out of the area near the airbox flange......"alright that can be good"... i couldnt really see where it was coming from but there was a fuel line there i a figured it must have got cracked or something even tho it is brandnew... so i turn off the gas and run it untill it runs out of gas.... (my theory used to keep it from flooding the crankcase).... i begint to take the airbox out.... this time i decided to leave the carbs in and just take the carb-airbox flanges off and then the air box.... as i take the left flange off(near the belt) i find my problem..... the airbox has mixed gas in it... and theres enought of it that i can see it is blue.... of course the airbox has a little drainage hole and thats where the gas was coming from!..... i tore the airbox out and thats where im at with that... there was enough gas in the belly pan that i started draining onto the floor, through a "centerless rivit"... so i am praying that im not leaking fuel ne where else... it really cofunses me because up to that point i never found any other sources for my mysterious oil in the belly pan.... i dont know enough about carberation to know what causes mixed gas to go into the airbox to even know where to go from here... so pretty much im going to sit back think about this for awhile.....on a side note... when i got it up to 7000 i left off and it backfired.... i just shit myself, cause it scared me.... im so lost on this thing now that i dont know if it is getting too much oil and not enough gas, too much of both, or what the deal is..... grrr, i just dont know....

im going to bed ill worry more about this later

[tyler440]

what are you finding out.. i take iot you havent started yours... i cant remember what state of resto its in

[SRXfromHELL]

Tyler
my first thought is to check the enrichment circuit (chokes) and make sure they are seated . also checkyour fuel line to your tank and inside the tank to the filter (mine was cracked inside ) also I found if I leave mine on a stand after running it , it seems to siphon fuel and fill the cases and exhaust with fuel . fuel in the pipes makes it very hard to start had to take mine off several times and empty fuel from them beforeI could start it .
try running it with the airbox off and make sure fuel is not running out the backside of the carb(s) i.e. bad needle and seat , float adjustment etc.a little dirt will cause a lot of problems . have you tried different carbs off something else to eliminate them as your problem ? as for mine its still in pieces have the motor almost done will have it in and running the next time I get home ( I hope) then I'll be right where you are . mine has the stock comet set up with yellow spring engages at around 5000 rpm shifts out at about 8600rpm and pulled like a bastard right past 10000rpm it ran really good except for burning down but that might be because of running 50:1mix trial and error I guess is the only way to find out keep in touch we'll figure it out eventually
Kevin

[tyler440]

"have you tried different carbs off something else to eliminate them as your problem ?"

yeah thats whats im going to do tonight.... im going to take the carbs off of chucks 540 and see what happens..... thats probably all ill have time for tonight....but ill let you know.... mine doesnt seem to be getting fuel in the pipes at all, certainly not enough to dump out.... it did when i first tried starting it because something stuck(float i imagine) and flooded the case really bad... i have looked at the chokes but ill do it again....

[Guest]

let me know how you make out . you can use mine if you need to either one 38ns or 44s
Kevin

[tyler440]

ok heres how the whole carb swap went..... pretty much the same as it was with my set up... my carbs had 280 and 290 main jets chucks had 2) 290's, my carbs had 40 and 35 pilots chucks had 2) 35... lastly chucks air screws are 2.5 turns out, mine were like 1/4 to 1/2 for some reason??(i think my setting is more right since, from what i recall, that is what the service manual calls for, but chucks vmax has no problems)... everything else ended up the same.... i had (at that point in time) my needles set with the clip at the top to try to compensate for the richness... the throttle response seemed the same... we had about 2 inches of snow so i decided that was enough to ride on and took it outside for the first time... it bogged down low and then pulled HARD once it got going.... i was definitly pleased with the power, but you have to keep it moving... also it still wont idle.... it seemed like it didnt want to rev as high as i expected ~8000 but i wasnt on it too hard it still pretty fresh, 15mi now....got back in the garage after al if this rippin around and pulled the plugs... everything was pretty clean but the top of the pistons have very tiny pits in them.... yikes... apparently its actually lean somewhere?!?!.... and that was that for that night... last night i duplicated chucks carbs and tonight im going to start it with chokes very loose and my needles in the middle position... we'll see how it goes... ill let you know.... oh i have all new fuel line... including in the tank

[SRXfromHELL]

I'm out of ideas ! but going to finish my engine today hopefully get it back in in a couple days and try it . maybe 38s are not way to go . have to try them I guess if not the 44s are going back on . will let you know what I find out if I ever get it together
Kevin

[tyler440]

*another update*

the left carb... filled the airbox with gas again so i changed the needle and seat... now it has a brand new one in it... well see how that goes... this things is being a real pain, good thing it isnt snowing its like 52 degrees outside now... and its only noon midas well hit 70 and melt what very little snow we have left

[tfin]

3 of 3 Vmax's I've had all had 1 or more bad floats.

Before you change the needles and seats, make sure the floats are right.

With the bowls off, fill the bowl with gas and make sure all floats float at the same level ie have the same amount of float sticking out of the gas. Make sure they are not at the stop on top of the rod, but free floating.

[Guest]

Hay Tyler Maybe this will help on the oil pump, the SRX oil pump is a richer pump then the vmax pump the way Yamaha measures there pumps is like this . the SRX is
min. at 200 strokes it puts out .040-.048 of an oz.
max. at 200 strokes it puts out .276-.308 of an oz.
The Vmax pumps is like this
min. at 200 strokes .042-.046 of oz.
max. at 200 strokes .183-.186 of oz.
so the vmax pump is really a little leaner , I also have both sleds and the SRX smokes a lot more then the vmax but mine has the 81 bottom end in it so with all the crank problems they are known for I think I will let it smoke . I hope that this can help you out.

[vmax-540]

Hay Tyler Maybe this will help on the oil pump, the SRX oil pump is a richer pump then the vmax pump the way Yamaha measures there pumps is like this . the SRX is
min. at 200 strokes it puts out .040-.048 of an oz.
max. at 200 strokes it puts out .276-.308 of an oz.
The Vmax pumps is like this
min. at 200 strokes .042-.046 of oz.
max. at 200 strokes .183-.186 of oz.
so the vmax pump is really a little leaner , I also have both sleds and the SRX smokes a lot more then the vmax but mine has the 81 bottom end in it so with all the crank problems they are known for I think I will let it smoke . I hope that this can help you out.

[Nye Racing #13?]

3 of 3 Vmax's I've had all had 1 or more bad floats.

Before you change the needles and seats, make sure the floats are right.

With the bowls off, fill the bowl with gas and make sure all floats float at the same level ie have the same amount of float sticking out of the gas. Make sure they are not at the stop on top of the rod, but free floating.

My 84 Vmax had the same problem!! One float was bad, I took two coffee with them with gas put one float in each can and left them over night. The next day one was on top and the other was on the bottom Problem fixed My sled would fall on it's face out of the hole and about 1/4 way down the strip it would come to life! After many tripps to the Yamaha shop and no answer! I decided the problem had to be the carbs, because the sled always run fine when it got opened up!