Jetting for restrictors
- Thread starter LeftTurn
- Start date
Raging Bull Engines
Member
My guess a spec gear red plate will be about somewhere between green and purple on jetting, but there are variables Depending on carb and track conditions. In fact, spec gear red plate is about the only class where depending on lap times/track conditions someone might change things like timing, jets, and valve lash while at the track while chasing the track .... Chew on that a minute. Chime in Big Chris because I am sure you have something useful to say about this.
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The red plate engines that I built, won the Maxxis Nationals and had a second and third. Won all but one Tri State race and the championship, Every Race in the big three challenge series, Two wins at Thanksgiving Thunder a second and a third and a ton of local races all in a 2 year period. I used .037/.038 mains and .026/.028 low speeds. On another note at these big races with a gear rule, If your engine won't turn 6700 rpm it will get waxed. Horsepower is not important, I would give up a 1/2 hp to gain 200 rpm.
1fasttiller
Member
Chris, I'm sure he meant years prior, there has been more than Maxx Daddy and Jr. Maxx Daddy
Renegade engines have been around awhile, and he knows his stuff. I really don't think he'd blow smoke up anyones backside...
Any tips on how one might get their red plate to turn 6700 with a gear rule? Have only been able to get right at 6200 out of ours in Jasper. Thanks in advance
Big Chris
Member
Chris, I'm sure he meant years prior, there has been more than Maxx Daddy and Jr. Maxx Daddy
Renegade engines have been around awhile, and he knows his stuff. I really don't think he'd blow smoke up anyones backside...
And I've been around since 2013
alvin l nunley
Site Supporter
I have some ideas! First thing you need to do is get that engine on a Dyno, find out where the engine starts running out of horsepower on the top end. With a fixed gear, I'm pretty sure the only thing that's going to make you go faster is more HP. Understand, everybody is looking to make more horsepower.
racinnut15xm
Member
With the gear rule you aren't looking for the most HP you are looking for good average HP after peak until as long as you can hold it. It forces the kart to run out of the typical power band the motor use. They are rapped out at corner exit and just making noise the rest of the straightaway
Engine is a clone red plate. (Cash) Peak horsepower is around 4500 rpms. At 6000 rpms, horsepower has dropped .5 hp or more. Builder says that motor will perform best keeping max rpm around 56-5700. Now, in jasper, red plate is on a gear rule 16/66, with 34.5" max right rear tire diameter. Our motor turned 6195 rpms all night with a 290-315 rpm drop according to the mychron5. With that said, my line of thinking was, what can I do to keep the motor closer to the "sweet spot"? (Haven't figured that out yet either) cant do anything gear wise or tire diameter wise to lower rpms. Now I read this post and renegade suggests that the red plate engine should be able to turn 6700 on these big, no lift, gear rule tracks. So which is it? And how would I accomplish it?
1fasttiller
Member
Its simple, on a gear rule track that is turning these little plate motors to death (Stupid IMO) you need the ability to turn it up or you will be getting outran! Renegade is spot on, at a big track like Jasper, you had better be spinning 6500+
Understood, but my question is how? Any advice on how to get that extra 300-400 rpms would be much appreciated
1fasttiller
Member
Very good flowing head, back timing off some and shim the springs right at the .815" height. That should get ya close.
Thanks alot! So it seems like it's all motor related. I'm not a motor guru and didn't build this one. But I can tell you what I do know... head is a 223 ,nka rules, so no porting. Timing is set at 38*. Carb has 39 main jet and 28 idle jet. I don't know how to check or set valve springs...
Renegade PM'd you
Cash builds a good competitive engine, got nothing bad to say about them. To get those rpms you first got to get the kart free, low rpm drops does not necessarily mean the kart is free. I have seen karts losing 100 rpm or less get lapped. Work with your driver to instill patience, wheel control and smoothness. Make sure you are spot on with setup, tires and clutch (yes the clutch is huge) The Vortex single or double disc are the best for Jr's in my opinion. Hard hitting clutches cause to much hysteresis and as they tend to be either locked or unlocked can slow the engine with too much slippage. Whether thats right or wrong I don't care, it's my opinion. Yours may differ.
On the engine, I have never had a red plate pull past 6300 on my inertia dyno. I have a 500lbs wheel and they just can't move it. But that doesn't mean It won't do it on the track. A gear rule red plate is built differently than a non-gear rule red plate. With a gear rule you look for rpm, Without it you build for torque. You can have one or the other, but you can't have both, Again my opinion and you know what they say about opinions.