300 SQUISH AND RK HEAD

[redbeta203]

I'm getting a lot of pipe bang with my rk head on decel on my 300. Ive tried two of his domes with different deck heights and still same issue. It has been a while since running my stock head and it is on a new top end (rk head didnt do this before replacing top end with B piston). Thinking it has something to do with squish. If I were to put the stock head back in what should my squish be and what is the best way to measure? Does this squish sound like it is related to my issue?

[LRM]

Not sure you are approaching this issue correctly. If you put the OEM head back on, the squish will be the same. I'd bet that it has more to do with jetting. What is your carb set up?

If you talked to Kels, I'm sure he can give you a carb set up for your conditions.

[redbeta203]

I was going to change the base gasket and check the squish with the stock head.

I talked to Kelsey and he told me to jet on the rich side but when I do it bogs and seems to make it worse. He also denied that pipe bang exists. It seems to get better with a 38 pilot and leaner needle clip. I have tried maybe 15 different jetting setups. I’m about all out of hope so thinking of just setting back to stock. Thing is I like the power delivery of the rk head.

[LRM]

I run this set up in my PWK 36 (Beta) and the PWK 38 (Husky), both have RK Tek heads. 38p, N8RH #3, 168M Husky is a 250. Tune bottom end with the AS. It works well in both. You can get the needles from RM/ATV. It comes from a 2015 KTM 300 6Days. You can get the whole series from them to fine tune the bottom. The piolet and main will be good. Just trim the tune with the needles.

[Darkside]

I was getting pipe bang on decel with my stock head on my 14 300. I started mixing 50/50 race gas and it helped a lot. I picked up a used rk head and tbh I don't notice a lot difference. The rk seems very sensitive to airscrew adjustments

[redbeta203]

Okay so maybe it isn’t the squish height. Since it was a custom head and Kelsey has the same year beta Id imagine it would be spot on or very close.

I tried some av gas 100 ll mixed with 89 non ethanol and it got rid of some surging I was getting when returning to idle but did not eliminate the pipe bang. I will try some c12 mixed 50/50 with pump I was just cheap and didn’t want to go with the c12 right away in case it wasn’t an octane thing. Kelsey said if the head was designed for pump then run pump...thing is it runs better with higher octane and my compression reads 210 which seems like a lot.

As far as needles go I have the Suzuki needle series and the jd needles. The blue needle in #3 is very smooth but the pipe bang is the worst of any needle I’ve tried. The starting diameter is also the largest so not sure if that has anything to do with it. I will check out those Ktm needles.

What about changing to a fatty pipe or something with a little more volume? Tried just about everything but really am reluctant to buy a new pipe as I like the stock beta pipe.

[LRM]

What you are describing is ALL jetting, not compression. But I suggest either using the JD Kit or the another choice and sticking with it until you get it sorted out. Your comments are indicating that you put it in try it and then change the set up without solving the tuning issues.

I had the exact same issue with my XT. I consulted Kels and JD, I gave you the set up from Kels already and this is the advice from JD;

"The off-idle is leaner with the red needle vs blue, but the tapers are the same in this jet kit's needle set. As a result, I was suggesting a richer tapered part using the #3 clip on red instead of #2 on blue. The air screw would probably need richening to keep the off-idle from being lean"

Quote from your post; "the blue needle in #3 is very smooth but the pipe bang is the worst of any needle I’ve tried." for above coment.

Either of these two jetting combo's will stop your pipe bang, just like they did mine. But the A/S is the final factor in the tuning to stop it. Don't be afraid to open it up if you need to. I'm running the Kels jetting I gave you and my A/S is 3.5 turns open. But both bike will start and set and Idle as they run out of gas. NO pipe bang on decel, with either one.

I would like to know if your RK Tek head was purchased used or straight from Kels? When you purchase one straight from Kels , he always ask you what fuel, elevation FUEL and mods you deal with. If you got it from Kels, what ever you told him at that time ab out fuel use is what you need to stay with. If you got it used , I would never run less than 91 octane.

I hope this help you solve your Pipe bang.

[redbeta203]

Okay I will give that setup a try. So I always thought past 2.5 a/s turns you should change jetting. The air screw is easy enough to adjust I will start there and see if I can tune it out. I’m glad my issue is not compression or squish because I was not looking forward to pulling my top end apart.

Yes, I did by the head new. I specified pump gas as it’s just easier and cheaper. Are you running the custom dome with a 1.2 base gasket stack or standard base gasket setup?

My settings right now are 38p, blue #3, a/s 1.5, and 170 main. Sea level to 800 feet. 40-50 degrees. Power valve with jd mod and 1 turn in.

Running a br7es plug gapped to .020”. Was thinking of trying an iridium plug but probably just adjust jetting now.

[LRM]

No, my motors are stock except the Heads and FMF Turbine core 2.1 SA. If you say with the JD needle, try the RED needle in the #4 clip position, Other wise, go with the N8RH #3 position.

[aj_mariner]

Squish does change jetting needs. Tighter needs more fuel to stay happy.
Stock dome is 1.9mm, Beta HC dome is 1.4mm, RK (pump gas, sea level) is 0.9mm.
The base gaskets are different between the RE and RR.
RE has a 0.5mm and the RR have 0.6mm or 0.7mm depending on the year.

RK Head needs the BPR7ES plug, possibly BPR8ES. BR7ES just never worked right.

At sea level, in winter temps...the RK was impossible for me to get perfect on the stock pipe. I had to wait till temps stayed above 50degF before really getting close.