yes the 480 fan again!

BUBS SRX

BUBS SRX

New member
ok i got some 38mm round slides for this now.
If anybody remembers it had 38flats on it before this mission started and ran pretty good at about 75 mph with 200 mj,42.5 pilot the air screw in all the way. ???
thats the billion dollar question why did it run so well with the air screw all the way closed off?
since then i broke the pilot jet off trying to go larger and had to locate different set of carbs because one was destroyed,I located stock set with stock jetting that dyno tech states are fine for said sled with slp single pipe. i looked up the link the good captain sent me and there was no recommended change for jetting. So in turn I tried to run it as is of course cleaning said stock carbs first,so it idles just fine but will not accept any throttle wit out backfire and hesitation nor will it move with out working the choke on and off.
Now I have the round slides installed It idles but again will not accept throttle,crack it open and it backfires,this is set at MJ 320 pilot 42.5 and 1 1/2 turns out, It runs better and idles at 2200 rpm but just seems wrong and wont idle down any lower nor will it move with out back fire.
any suggestions would be great cuz I am about to toss a stick of dynomite in this biotch and blow it the F up!

Am I wrong in thinking it may have a seal leak???
 

Was it an actuall "air" screw or a "fuel" screw?

on the flats it should have been a fuel screw I believe?

typically an air screw for example, has a effective range of 1 to 3 turns out..if you find a motor runs best outside of that range, it would indicate an incorrect pilot jet size...
so lets say the motor ran best with an "air" screw in LESS then one full turn out..

that would typically indicate too small of a pilot jet..(you`d be basically richening up the air/fuel ratio, by cutting down the air...

now if a aire screw ran best set at more then three turns out..that would indicate too large of a pilot jet...

so if it was/is truely a carb related issue...and it ran/idled best with the air screw all the way in...then that would indicate that the pilot jet was either partially plugged, or much too small..

If not carb related..then I`d lean towards either a intake leak..improper fuel level in the float bowl, or insufficient fuel flow to the carb...


this assumming the comp is good, no engine case leaks etc...
 
Bubs, 80s vintage phazers were tough on seals. U may indeed have a seal problem. Motor needs to be pressure tested. If nfg check the pto and mag side crankshaft runnout, cracks in carb boots, etc.
 
i believe that to be the problem,I cant get it to run consistent with any carb configuration jetted high or low meaning(300-147.5 mains) stock carbs or flat or round.i have tried every thing i can think of to get it to run smooth and idle but it insists on staying at 2500 rpm idle air screw in 1/2 turn to 2 1/2 out its unreal.Idle fine crack the throttle and blah POP!
 
Well its leaving my hands now,its going to the well known Doc Fangs shop for a better analisis. Im thinkin if he cant get it running correctly no one can. Im done trying to figure it out
 
Its toast!crank seals were fubar,it had water in crankcase at one time and the bearings were S H O T. No wonder it was so friggin loud,two different size pistons and they were about to melt so thank goodness i never ran it over 5 minutes at a time. So ther was my reason that the air screw was closed off completely and still running. anyody got a fan motor for sale???this chasi is to nice to scrap or part
 
BUBS SRX said:
Well its leaving my hands now,its going to the well known Doc Fangs shop for a better analisis. Im thinkin if he cant get it running correctly no one can. Im done trying to figure it out
Click to expand...

Doc Fang has a really sweet VMAX-4! I saw it up at the Port Huron Chilifest.
 
Yes they have some nice sleds there,him and his son are really nice guys. Straight up and to the point,honest in their assesment and evaluation of Jerrys sled. They did not in any way try pumping him for money and explained all his options and directions to go with that sled. Im going to take my srx to him to true up and weld my crank plus reseal it for me. I cant say enough,both are real genuine good guys.
 
And about the vmax4 it is real sweet and low,he had it up on the lift motor out broken circlip in wristpin destroyed a cylinder for him. His 440 booboo is a nice piece of work too,the chain is exposed no cover. I suppose thats for easy gear swaps and lower weight. They had a real nice gpx too of course all mods and some other stuff to. Im glad to have met them for sure they just make ya feel comfortable talkin about sleds or what ever.
 
Yes the crank seal and bearings were shot,i should hace recognized the growl coming from its core while it ran but i was not familiar with fan motors and was told they were loud. Im glad it didnt grenade in my lap flying across the lake @ 75 mph the one time i had it there.
 
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