Custom/Hybrid Unreasonably high compression numbers

[Brian_216]

I got a brand new snap on compression tester, checked and I have 230 psi.. I am at 1400 feet and plan to ride in NC this weekend at sea level. There is no detonation on anything, I pulled the head and checked. The domes that are in it are 28cc flat top domes according to the part number. I see ADA only lists a 30cc in this configuration. What are my options? I dont think 2ccs is going to get me to 190. I sent an email to Paul at LPW to see about cutting the domes. Will straight av gas be safe?

Thanks

 

[Byeai]

jetmaniac told me if its new motor u gotta break it in before u check it

Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

 

[Matt_E]

Straight avgas will not be safe. It's only about 100 octane. You need probably 110 or more.

 

[DAG]

Is it a DASA PV motor? Kyle says to check with PV's open. Dropped mine from 200 to 185

 

[O2VW1.8T]

We need to figure out how to get E85 to work in our ski's. I would imagine the jets would have to be much bigger.

 

[Brian_216]

Is it a DASA PV motor? Kyle says to check with PV's open. Dropped mine from 200 to 185

Paul emailed me back and told me the same thing. Heading out to check now. Yes it is a DASA PV 8mm

Edit- I just tried valve open and valve down. Im getting the same numbers?

 

[kx454]

After a motor is broke in they make more compression.....


Brian did you check what your motor was running when I rode it?

 

[Brian_216]

Yea, on a crap sunpro gauge. said 205 Snap on is saying 230

 

[jamesgunter68]

Don't always trust a snap on gauge they go bad quite a bit

Try with a few different gauges

 

[Brian_216]

I was only trusting it because it just came off the big red and white truck, new in the box.

 

[kx454]

Weve got two craftsmans at the shop that are consistent with each other....god knows if they are accurate haha, you can try them. Is there a bunch of unburied fuel or oil in the motor? Years ago after a rebuild I had a bunch of break in oil in the cylinder and it gave me something like a 240 psi reading

 

[jamesgunter68]

I was only trusting it because it just came off the big red and white truck, new in the box.

Snap on gauges is all we use at work but I've seen brand new ones go bad or faulty ones

Their gauges arent really made by them? They just put their name on them

 

[Brian_216]

Yes, I had it out for a rip to try the new carbs and noticed its still a little rich on the bottom, so idling into the trailer it loaded up a bit. We were doing the test after the ride. So un burnt fuel could be the culprit. Ill try again tomorrow before we pack up for the trip. I dont want to have to buy race fuel!

 

[Brian_216]

I double checked the squish. It's .047. I'm stumped. Maybe the snap on is way off? I'm now getting 220 since its dried out a bit

 

[jamesgunter68]

im running 37cc domes and 185-190psi

 

[Brian_216]

I tried another tester and got 200. There is no detonation marks after 30 gallons of 93. I think the snap on man owes me a new one!

 

[jamesgunter68]

I tried another tester and got 200. There is no detonation marks after 30 gallons of 93. I think the snap on man owes me a new one!

i would think so too
the last time they calibrated ours they took 5 out of 6 from us

 

[NVJAY775]

E85 would be cool. I think I read it's hard on seals, doesn't mix well with two stroke oil.. Not sure though. But it sure would be nice to not spend as much on fuel. But also heard E85 requires about a 30% richening, so the savings goes away a little, but even at that it would still be cheaper. It's $3 something a gallon, vs 10.50 for sunoco 110. A lot of import tuners run it here, so they can run higher boost / compression and not have detonation issues.

 

[Matt_E]

The 30% richening (lower energy content) would also mean that a 3 gallon tank is now effectively a 2 gallon tank. No thanks.

 

[NVJAY775]

Good point. Dammit!! I'm starting a new thread.