I am trying to gain some performance back due to some mods that aren't quite working out as I feel they should. Doing a little troubleshooting before I finalize on a conclusion on what needs to be done.

I think I am lean on the jetting (discussion in a previous thread) but I went ahead and checked the compression just to be sure that wasn't an issue.


I got an initial reading of 90psi with the battery alone. This was due to not spinning fast enough to disengage the decompression mechanism. I then hooked up a pair of jumper cables from the battery in my Suburban to the Raptor battery. The starter really didn't seem to be turning much faster, but it was enough to over ride the decompression mechanism, at least partly. I got a reading of 155-160psi. This reading is within "normal" but on the low side. I then put a little oil into the cylinder to see if that would bump up the compression any and it didn't have much of an effect. I can pretty safely conclude then that my piston/cylinder don't have any abnormal wear and that my valves are good. My valves are set at .127 intake and .178 exhaust so they are in spec.

My question is this: The service manual says that hi normal is around 190, standard is 180 or so and the minimum is 149psi. I have done a search and no one has ever achieved these numbers, at least that have been reported. The highest I can find is about what I got, 160psi. Does this seem right? 14 mins, Moose, anyone?

Also, I didn't charge my battery first or anything, just attached the jumper cables and tested. I did have the throttle at WOT as well. Would it be better to use a battery charger first (to charge the battery fully), then put it on boost and give it a try? Let me know if anyone has any experience.

At any rate, I don't think this is my problem. It seems like it is just jetting but the lower reading scared me a little until I saw that everyone else was within the same ballpark.

Thanks

 

Anybody?

 

bump. Sorry to be a pain!

 

I missed the early part about your jetting , but what seems to be the prob? What mods do you have? What jetts are you running? Be glad to help anyone who can type that long message.[img]i/expressions/face-icon-small-wink.gif[/img]
Not saying I can but I'll try.[img]i/expressions/face-icon-small-happy.gif[/img]

 

Here's a link to the earlier thread: http://forums.atvconnection.com/mess...did/328095.cfm

Basically, I am running a little lean and am wondering if anyone has any suggestions. I've ordered DJ 155, 160, 165, 170, 175 and plan to try the 160, 165 needle on third clip.

We'll see.

I am also wondering if any one has any input on the compression measurement.

Thanks