81 srx 540 is gutless

tyler440

tyler440

Member
Joined
Jan 20, 2006
Messages
363
Age
41
Location
Clarion, PA
Website
www.vintagevmax.com
can some one tell me why my 81 srx with a 540 motor is no top end(due to clutching), and a low end engine bog? i know that is vague so here more info...

it tops out at about 55-60 at 7000rpm, with a light purple comet spring and two shims, the secondary is wound at c-2

have have stock vmax jetting with the excepting of 3.0 slides...
the change of slides took the idle from 1500(2.5's) to 3000(3.0's) and it also seemed to help it get out of the hoel better....

i was wonder what the 81 chaincase will do with the 540 clutching... is the gear in a 81 higher or lower than the 540's?

i dont know what other types of things you might want to know.... just ask ill tell you
 

HAS NO TOP END BECAUSE YOUR ONLY TURNING 7000 RPM. 540 VMAX PEAKED AT 8200. YOUR WAY OFF. TAKE YOUR SECONDARY UP TO C-3 AND SEE IF RPM COMES UP. NOW GEARING, VMAX 540 WAS 18-33. THIS SLED IS A 81 SRX I BELIEVE GEARING WAS THE SAME. POST YOUR JETTING. 3:16 (yammie tony)
 
81 srx stock gearing was 17/31

what weights are you using in the comet clutch?


the bog you have is it a lean bog or rich bog? you can check by hitting the gas and slightly opening the choke lever, if its better then its lean, worse its a rich bog.

are the carbs in sync?
 
i realize my top end is suffering due to lack of rpm, but why would it lack rpm with all stock settings..... 290 mains 135 pilot jets, needles are in the middle position, i did change the slides from 2.5 to 3's that seemed to help the low end rich(i believe) condition, i also turned the air screw in from 1/2 turn out to a 1/4 turn out in an attempt to lean out the low to mid range a bit... i have no problem starting with out choke it starts in 1/2 a pull so this is another reason i believe it to be rich. vmax540 (uncle chuck) and i spent a good 7 hours yesterday double checking adjustments, settings and what.... we had poor snow conditions but i still wasnt able to go over 60mph in 1000 feet and my 13 year old cousin toasted me on his phazer I NEED HELP QUICK!!!! HAHAHAHAHA
 
oh yeah and the carbs a in sync, we didnt actually use the vacuum gage method though, maybe if chuck reads this before he leaves work he will bring the vacuum gauge he has there :)
 
sounds like the front cluth spring has gotten week have to checked comprresion to make sure you have enough power to turn rpm my freind had one and it would fly
 
i honestly dont know what the compression is but since the motor has about 50 miles on it tops, i would certainly hope im alright in the area!! stranger things have happened i suppose, i mean last year i managed to put like 25miles on it with the slides in backwards!! (they were slides for someother carbs)
 
i would do a compression test just to cover bases inspect front clutch remove the cover and see if the front spring is collasped also make sure a choke is hanging up that could case a bog my buddies with the factory twin pipe would pound my stock phazer
 
on the air screws, out is leaner, in is richer.


what clutch weights are you useing? the wrong clutch weights via too heavy for the spring can cause you low rpm.


Are the choke plungers set right? you can pull up on the cable right at the carb adjusters and you have about 1/8th inch slack??, the cable comes up out of the adjuster slightly right?

do the sparkplugs have any color on them after your running it in the field? will it idle and keep the plugs dry or are they soak and wet with fuel/oil?
 
the chokes are set rigth like i said we spent about 7 hours yesterday double checking it.... i dont know much about the clutch weights, i am also going to try a different purple spring with 3 shims... i forgot to mention that the primary engages at 4000 with a purple spring and on shim.... i understand thats too low.....

are you positive that turning the air screw OUT leans it? this is on mikuni 38 round slides
 
If the screw is behind the carb slide(airbox side of carb) its a air screw, so yes, turning the screw out would allow more air in and lean out the mixture.

If the screw is located in front of the slide(engine side of carb) then its a fuel screw and it works opposite, turning it out would make it richer.

again, what do the spark plugs look like after you ride it around? and after it idles??


well if you dont know what clutch weights are in your own sled, neither do I, so cant help if you cant provide information to work from. If you have weights that are too heavy, its gonna be low on rpm, especailly if the spring isnt storng enough. You have to remember we are trying to fix a problem we cant see or hear or touch, so you have to be our eyes, ears and fingers,need information to solve a problem.
 
if you have a comet clutch on it, you should have A3 arms in it with a silver spring
 
alright i seem to have it running alot better! here what i did.... first off i put a "darker" purple sping with 3 shims in the primary... this didnt really seem to have much of an effect of engagement(about 4000) it did however seem to get out of the hole a little bit better.... still no top end.... then i put on another secondary clutch(still from a vmax tho) however this one was set to A-2 from previous testing of a phaser...and turn the air screw out to 5/8 out... you were right it comes out to make it leaner...i read the book this time.... take her our in the field... now we are getting somewhere.... now its getting a bit over 7000 and probably about 60 or so mph... back to the garage to fix this pesky lowend bog..... so i take the pilot jets from 40 to 30(previously i said they were 135 i was confused with power jets)... back out in the feild.... loook out it seems to be tearin' it up now it doing about 70 at 7500 or a little more rpm in 1000 feet.... still have some more clutching to do... probably will try b-2 or c-2 and see what happens... ill let you all know....
 
102 or 108???? Completely different animals to clutch when it comes to the Vmax 540. You guys know the routine when it comes to them. It's been all over Vintage Vmax. It sounds to me like you are going through the Vmax 540 108 blues.

If you have the right 102 on there (to be stock) you should have the white/yellow (Yamaha) spring in it with A-3 weights. Pink spring in secondary set in C-2 with 40* twist. With that setup you should be engaging at 4000-4200 with no shims and be shifting at 8000-8400.

If you are running the 108 (you are arn't you?) your belt is probably bottoming in the secondary before it reaches the top of your primary and streatching your belt (wants to lay down at 7000 and burn mark at top of primary). If that is the case you will need to remove some material from the back side of your secondary helix (1/8" to 3/16") so it can open farther to allow the belt to drop deeper in it, thus allowing the belt to reach the top of the primary without streatching. If your belt is streatching because of the larger diameter 108 clutch you will never fix it with springs, weights, shims or adjustments.

opsled
 
oh btw tony my sled is haunted by like 30 of the evilest spirits you ever heard of and doesnt ever like the settings chucks has..... and i think chucks vmax has a 108 on it but i cant remember even though the two sled sleep 15 feet from eachother they dont like the smae things for some reason
 
the chart i look at was hand written but it showed a-2 a step tighter than c-2?? and i am running the 102 phil, i have a purple comet spring in it.... i dont really liek the fact that i have 3 shims in it but ill continue to to tweek, god knows chuck has enough different springs and and such i should be able to find something that works.... also i want to REcheck my center to center distance tonight... thats one thing i skipped... whas does everyone think of having to go from 40's to 30's in pilot jets... it seems to really rip and tear with them so this will be the longest day at work ever!
 
JUST SO YA KNOW THE COMET PURPLE YOU NEED IS PART # 207758 FOR THE 102. ALITTLE CONCERNING YET IS YOUR ENGAGEMENT SHOULD BE HIGHER THAN 4000 WITH THIS SPRING WITH THREE SHIMS. NOW I WANTED YOU TO ASK YOUR UNCLE CHUCK WHAT WAS IN THIS SLED FOR CLUTCHING NOT WHAT WAS IN HIS. 3:16 (yammie tony)
 
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