RPM problem

EricMichael

EricMichael

New member
Joined
Dec 25, 2005
Messages
543
Location
Presque Isle, ME
Ok guys i'm running a slp viper, with lots of traction and 20/39 gearing. Problem is when I stab on it out of the hole it bogs for 10 feet and then rips. Bought a green white green spring with 3 shims, silver secondary. The thing launches at 4500 rpm and I was told i need 5000,5500 rpms to not bog with my type of traction. Talked to the local dealer today about it and he told me to drill the inner rivet out of my 8EK weights and this would cure the problem. Talked ot him about bigger pilots like a 55 and he said not to go above what i'm at right now (47.5). So what do you guys suggest?i'm lost!
 

Hmm... sounds like a classic lean bog to me. Sure, revving up to 5000 + will cure your problem when you get there... but it's not the solution. I would say go up at least one more size on your pilots... stock is only 45 anyway, you're only about 1 step up.
 
slps jetting recommendations are about spot on. Run what they suggest and go from there.
 
47.5 pilots and 2 turns out on fuel screws should be fine, if you have traction like you say you do ,youd want a 5000-5500 rpm launch to take advantage of it. I would be running a set of 8ca weights over the stock 8ek weights for 500ft drags. You need to watch for a overshift condition, if the sled takes off and slowly revs up then actually loses revs for a short distance, then gains revs again, its simply overshifting, this is very common on grass racing, this is due to the clutchs getting ahead of the engine, use a silver secondary spring around 80/90 degrees with your helix.
 
mrviper700 said:
47.5 pilots and 2 turns out on fuel screws should be fine, if you have traction like you say you do ,youd want a 5000-5500 rpm launch to take advantage of it. I would be running a set of 8ca weights over the stock 8ek weights for 500ft drags. You need to watch for a overshift condition, if the sled takes off and slowly revs up then actually loses revs for a short distance, then gains revs again, its simply overshifting, this is very common on grass racing, this is due to the clutchs getting ahead of the engine, use a silver secondary spring around 80/90 degrees with your helix.
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Yeah the dealer said that I should run the 47.5 pilots. He told me to drill out the inner rivet on the 8ek weights so I did and it still doesn't seem to help so i'm going to put the rivets back in and get my engagment up to 5,5500 because it hooks up way to good.(diffrent spring?) I'll go with the 8ca weights but how much rivet weight?Theres nothing you can do to the stock weights?well thanks for your advise seems accurate.
 
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the 8ca is alot more aggressive profile for drag racing then the stock 8ek weight is, you should be able to run real close to the same amount of weight you have now in your weights. I would suggest you run a white maxx perf primary spring, this will raise your engagement speed as the spring your using now is only 45kg start, the aftermarket spring is 60kg start. Hauck sells a orange primary spring that would also get you closer then now(55/225). You should also be around a 21/40, 20/40 gearing in chaincase.

you have your fuel screws in bottom of front of carbs turned out 2 turns from lightly seated right??
 
When you run the 8ca,s most of the weight will be in the tip. You might want to try 8ab,s for a little more adjustability. Same profile but 2 grams lighter.
 
mrviper700 said:
the 8ca is alot more aggressive profile for drag racing then the stock 8ek weight is, you should be able to run real close to the same amount of weight you have now in your weights. I would suggest you run a white maxx perf primary spring, this will raise your engagement speed as the spring your using now is only 45kg start, the aftermarket spring is 60kg start. Hauck sells a orange primary spring that would also get you closer then now(55/225). You should also be around a 21/40, 20/40 gearing in chaincase.

you have your fuel screws in bottom of front of carbs turned out 2 turns from lightly seated right??
Click to expand...

two turns as in 4 turns of a screw driver??talked to a local grass dragger and he says to get the hauck spring as you did, have that on the way, possibly a couple shims he said. Was told to use a straight 34 helix with a redish/pink secondary?anyone heard of this working?he said it may work better than the 51/45 with a silver secondary..going to try them both anyway..
 
2 turns out from lightly seated will be 2 complete 360 degree left hand revolutions of the screw.
 
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