Help, low compression after new top end

Baja 252

Baja 252

Location
LOTO
Dasa 1000, new pistons, rings and bore. Dasa did the work and all went together great, turns over fine and sounds normal turning over. For the heck of it I checked the compression (good gauge) before I put in the water and it's only 150!! It should be 180 - 185. I've never seen this before, but I've never re-built a Dasa before. I'll talk to Kyle on Monday, but I wondering if it would it be normal for the compression to be low before the engine is started and broke in. With the extra oil on the rings from the assembly I would think if anything it would have higher compression than normal??

I don't want to start it and run the risk of damage it if somethings wrong.
 
Harbor

Harbor

Location
Stockton
Last 3 engines I tested before and after ring seat compression on went 10 psi higher after ring seat. A 4th with old bore and new rings was higher due to rebuild oil like you mentioned then dropped 10 psi after running the engine.

Edit: forgot the most recent one, it went up 20 psi after the rings seated. I'd prolly wait to talk to Kyle too, can't hurt
 
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Christian_83

Christian_83

Xscream
Location
Denmark
1. did you do a compression test on the DASA engine before you rebuild, to confirm that it did have in the 180 psi area?
Did you messaure the base gasket from old setup and new setup?
Did you messaure squish band before/after?
 
C

Coache11

Location
Lakeville
Coache98 said:
this is Irrelevant but how can I post on this forum lol. Thanks
Click to expand...
Also, great ski man I've actally have been looking into the xscream complete skis such as the 900. Seems like they are a big flat water freestyle company. The question I want to post is about those krash skis, am I missing something because the price is just a little more than a new superjet. Thanks in advance and sorry I can't answer your question I'm new to the site
 
Harbor

Harbor

Location
Stockton
xXx Octane xXx said:
Any chance you’re leaking past the o-ring or rubber gasket on your compression tester?

I would order these and try again with the crush washer in place of the o-ring: https://www.mcmaster.com/#97725a105/=1cmqaym
Click to expand...

Good point! This happens to me a lot and drives me crazy. I should try these too

Unrelated but I'll add the short reach hose tip gave about 7 to 9 ish psi loss over the correct long reach hose adapter.
 
Baja 252

Baja 252

Location
LOTO
Sorry I've been busy. Took the head off, all looks fine with cylinder walls, head and O rings. I'm going to be removing the cylinder to measure and check things out further.
 
Christian_83

Christian_83

Xscream
Location
Denmark
But, did you compression test your engine yourself, before rebuild and got a reading of 180psi?
Or is this just something you have been told?
 
Baja 252

Baja 252

Location
LOTO
We bought the engine new. When new, it was 180/180 and for the next two years it held the 180/180 reading. As expected at around 50 hrs the compression started falling, indicating it's was time for a new top end.
 
FX1 696

FX1 696

Location
Wisconsin
Coache98 said:
this is Irrelevant but how can I post on this forum lol. Thanks
Click to expand...

I can't tell if you're kidding or not because it seems so self explanatory.. But I'll help out a helpless nube just incase you're serious.

When you're in the section you want to post in, example "General", click the orange "Post thread" button in the upper right. Picture below.

1526062009437.png
 
Christian_83

Christian_83

Xscream
Location
Denmark
Baja 252 said:
We bought the engine new. When new, it was 180/180 and for the next two years it held the 180/180 reading. As expected at around 50 hrs the compression started falling, indicating it's was time for a new top end.
Click to expand...
Okai good stuff.
So both holes read 150 psi?
Did you give the pistons to the guy, that made the new bore in the cylinders?
Check ring gab ? Check squishband?

One thing that REALLY fooled me, and i only discovered by coincidence 1 year later, was a little rusty OEM starter and 1 year old battery cables that got a little bit of saltwater and a semi worn battery
My engine at the time, TPE 900 CO, should give around 190 PSI, but i was only getting 170-175. Hmm wrong, but the engine ran super good. We didn't understand it, because the starter system ran good and sounded healthy, with good RPM.
Fast forward 1 year, my starter started crapping out, i bought a new OEM one. made all new cables and bought new battery. Guess what, the starter system ran even better lol AND my compression gauge read 200/200 psi lol !
 
Roseand

Roseand

Ready to RIP
Site Supporter
Location
Wisconsin
Christian_83 said:
Baja 252 said:
We bought the engine new. When new, it was 180/180 and for the next two years it held the 180/180 reading. As expected at around 50 hrs the compression started falling, indicating it's was time for a new top end.
Click to expand...
Okai good stuff.
So both holes read 150 psi?
Did you give the pistons to the guy, that made the new bore in the cylinders?
Check ring gab ? Check squishband?

One thing that REALLY fooled me, and i only discovered by coincidence 1 year later, was a little rusty OEM starter and 1 year old battery cables that got a little bit of saltwater and a semi worn battery
My engine at the time, TPE 900 CO, should give around 190 PSI, but i was only getting 170-175. Hmm wrong, but the engine ran super good. We didn't understand it, because the starter system ran good and sounded healthy, with good RPM.
Fast forward 1 year, my starter started crapping out, i bought a new OEM one. made all new cables and bought new battery. Guess what, the starter system ran even better lol AND my compression gauge read 200/200 psi lol !
Click to expand...
^^^^^ look into this. Had a very similar issue with my setup. Battery had enough juice to start the motor but not enough to max out the compression reading. Hookup a jumper pack and the compression shot up 30 psi.

Sent from my SM-G920V using Tapatalk
 
Christian_83

Christian_83

Xscream
Location
Denmark
Roseand said:
^^^^^ look into this. Had a very similar issue with my setup. Battery had enough juice to start the motor but not enough to max out the compression reading. Hookup a jumper pack and the compression shot up 30 psi.

Sent from my SM-G920V using Tapatalk
Click to expand...

Yeah i used a jumper as well, but with starter being worn a bit and cables had some flaws, the system couldn't transfer more amps :(
 
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