Compression low, gonna put in a new top end

CO 2.0 · Mar 1, 2017

Few rides ago I checked compression, it was 105psi both cylinders. Now it's 100psi mag, 105psi PTO. Fully warm at 5000ft. Seems a bit low to me. Better to be safe than sorry, so gonna put a new top end in and re-hone the cylinders. Does anyone know what size hone I need?

mtncat1 · Mar 1, 2017

take it to a machine shop to hone it , it needs a ridge diamond hone , do not use a ball hone . it will cost you around twenty buck .

CO 2.0 · Mar 2, 2017

Do i need to re-nikasil the cylinders if they look ok or just do a diamond hone? 1200 mi

BILTIT · Mar 2, 2017

If the nikasil is fine you do not need to re-coat, just a hone.

Majority of time just a hone is required.

Merlin · Mar 2, 2017

Before you do anything the PTCW clearance of the new pistons to the existing cylinders should be measured.

If excessive, the cylinders will need to be repaired / replated which is out of scope for the average machine shop.

CO 2.0 · Mar 3, 2017

Cylinders look to be in good shape. Just a couple small spots where the cross hatch is worn. No Scoring. Pistons didn't look that bad either. Should just need a re-hone.

Angermangement890 · Mar 5, 2017

I would suggest sending the cylinder to Indy Specialties for their HG7 honing procedure. Be sure to send the pistons as well so they can check/fit then to the bore.

B&M Fabrications · Mar 5, 2017

I'll second Anger-mange-ments opinion. You will not be disappointed with the HG7 from Indy Specialties.

Sent from my SM-G928V using Tapatalk

CO 2.0 · Mar 5, 2017

What is involved in hg7? I tried calling Dan last week but he was out till this week sledding. I wanted a quick turn around so I could break it in next weekend. So I sent it out to SLP on Friday. No one in town would touch it cause of the nikasil. Slp said diamond hone was too aggressive and would take off too much material.

tdbaugha · Mar 7, 2017

If you read Dan's posts, the next best thing compared to HG7 is factory honing with mileage on it.

So you can spend another $500 to get better cylinder plating, or just throw in some new pistons and call it a day.

wellfed777 · Mar 7, 2017

would you mind tell us what the piston clearance was
when you tore it down ?
maybe post pics of pistons ?
thanks

CO 2.0 · Mar 7, 2017

I didn't even measure. Just wanted to get the cylinders sent off as quick as I could so I could get them back to ride. I'll take a pic of the pistons. The one with lower compression had some scuffing on a spot on the top ring.

CO 2.0 · Mar 7, 2017

wellfed777 · Mar 7, 2017

1200 miles of turbo ?
how much boost ?
thanks

CO 2.0 · Mar 7, 2017

700 mi stock, 500 boosted. 5psi spring with 1-2 gallons of 110 and non eth 91. Ves gold

diamonddave · Mar 8, 2017

Are you going with OEM pistons?

CO 2.0 · Mar 8, 2017

Yeah.

Just to compare, my buddies 2015 Cat was 126psi both cylinders on a cold motor. So I don't think my gauge is messed up.

Sage Crusher · Mar 8, 2017

Probally good that your tore it down at your elevation results.
My shop is at 6,950' and checked 2 Axys both stock one @ 400 miles the other @ 1200 miles and both are 105 @ this elevation.
My silber Axys 800 stock miles and another 500 on the turbo total 1300 miles am @ 105psi...

CO 2.0 · Mar 8, 2017

So down at 5000ft youd be roughly 110+ psi then. Thats good to know. Thanks

sumtinwong · Mar 10, 2017

so what is Indy Specialties HG7 honing procedure?? is it better cylinder plating?

Compression low, gonna put in a new top end

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