I'm thinking that definitely has something to do with it. Axtell supplies JE flatops that displace 3 ccs, before any valve reliefing might be done. depending on the head gasket selection, I think this might be on to something. Cannot have 210 ccp with this combo. I just plug numbers into two diff calculators, not knowing altitude looks like 9.8:1-9.9:1 under 180ccp. Sounds to be the problem to me!!

 

Not sure about the piston specs but if the JE dome is 3ccs before valve reliefs, I would guess the valve reliefs for 1.9 and 1.65 valves would reduce dome volume by at least 3ccs. So using 0.00 as dome volume, I calculate 10:1, 9.29 corrected and 193psi; sweet spot for those cams and the motor should run good with those numbers.

Corrected and cranking CR are functions of the intake valve close; the 570G intake closes at 40*.

When Coyoted started having problem originally when the motor was first tuned, I thought it might be compression related and bugged Coyote about it. He had two different compression tests run, I believe by different techs but not sure. Both produced 210psi, front and back.

I don't have any idea what the problem is but don't think the problem is low compression.

 

I need to find out more about the pistons. Chaz told me my CR is 10.6:1. I did the first compression test at home, just to have a baseline. The tuner confirmed it.

 

I must have mis typed that. When i ordered my cylinders and flatops i was told by ron that they were JEs and were -3ccs, 117 ci JE pistons were/are -10ccs. Maybe the wrong pistons were installed..... Also the cams used were andrews 67gs, with a 48* intake closing. Andrews told me their choice for compression on that cam is 10.3:1 which is what i did. I really need to get to a dyno just so there is a comparison on our builds.

I'm not saying low compression IS the problem, but I would definitely sort it out. If using Axtells JE pistons at -3cc, possibly valve reliefs cut, possibly -1-2ccs, typically people use a .030 head gasket, i used a .040 and if he did it'll be even lower, .030 with the above 9.8:1ish .040 9.6:1ish again depending on altitude. If either is the case, there WILL be a lack in performance. 170-175 ccp. Something is still not adding up.

Sucks that to check some of this the heads will need to be pulled.

 

If it cranks 210-CCP on both cylinders and has been verified by another guage, low compression is definitely not an issue. With that 67g cam, and it's timing events the compression is sky high for a pump gas street bike!! Closer to 11.25:1 static, and almost 10:1 dynamic.


K.

 

This is the map that he said produced the most power. He said he took a lot of timing out of it.

 

Read all the posts guys. I know 67G is in the Coyote's signature but, according to his previous posts, the S&S 570Gs were installed.

 

Now I have to re-read the posts. Sorry if there is any confusion, but they ARE 67G's. I know this for fact, I had them in my hand a few weeks ago when we were checking them.

 

That isn't what you previously posted but does make a big difference. The intake close on the 67G is 48*, much later than the 570G. If Matt is correct on the piston dome volume of -3cc that would drop static CR to 9.8, long way from 10.6 per Axtell. Corrected CR drops to 8.7 and should be up around 9.3 and cranking CR under 180; OEM territory and would explain why the tuner couldn't dial in much timing; the motor doesn't like it.

Sure doesn't square up with the 210psi you previously posted and, as Matt pointed out, no way should CCR be 210psi with the above combination.

agree with Matt that compression could be the root cause of the poor performance but until we get the data right, can't say for sure. All we know as absolutes right now are the cams and the chamber volume. Unknowns are piston dome volume, deck height and head gasket thickness.

It would appear that your previously posted compression test results are incorrect.

 

When Darkhorse did your crank for you, was the pinion shaft indexed or checked. I know runout was checked but a twisted or misaligned pinion shaft could give you the high CCP readings on both cylinders equally. Where did the crank come from again? Too high compression would indicate why the tuner had to set the advance curve so low. Higher compression speeds up the flame front so ignition needs to be retarded. Low compression engines tend to advance timing more because the slower flame travel builds cylinder pressure slower.