Thread: GP1200R Compression....
05-08-2010, 06:02 AM #1
Hi guys, sold my GP800R an looking at 1200's.
What is the recommended compression specs for an engine with approx 35hrs since rebuild?
I tested one today, still STD, has 76hrs but was rebuilt by North Coast Motorsport at approx 40hrs, not sure why that soon but nyways. Crank replaced with hotrod crank all new brgs an gsks, WSM piston kits etc.
I done a comp test when I viewed the ski with 112psi approx on all pots.
Is that ok or should I be hesitant?
My 800r was 130psi on both....
05-08-2010, 10:40 AM #2
depends on your gauge...but if it was even across all three thats fine for stock....
05-08-2010, 04:59 PM #3
Thx BoostCrzy.... Yeah it's a new guage so it should be pretty close.
Just wasn't quite sure, especially cause it had the rebuild so early. It ran fine but will check a few others out yet.
Got a Riva rideplate an R&D grate in the garage already and will seal the shoe up and fit the plate an grate, then later a Solas prop. Just those few extra should make a noticable difference yeah..?
05-08-2010, 09:08 PM #4
yea the intake grate and a rideplate will be best bang for your buck....then get the carbs rejetted..cut the head....and put prop in her...then your golden...
05-08-2010, 09:12 PM #5
05-09-2010, 12:51 AM #6
Sweet. Will do. Do u have to change the hsg when u do the om prop?
Well I've been looking at the 1300's also lol, it always seems that when u are at your spending budget an u see the next bigger thing ie 1300 for jusssst that wee bit more, u think meh what's another coupla grand haha...
Thx heaps again for the support guys
05-21-2010, 06:05 PM #7
- Join Date
- May 2010
if your not using a snap on tool. add 10 psi at least for using a screw on compression tool
05-21-2010, 06:50 PM #8
GPRocket, 112psi is very normal for compression on the 1200 motor. The range is around 110-115 for a stock motor depending on a lot of variables. Like Jack said, it's most important for them to be fairly even across all 3.
I've gotten to the point where I don't pay a whole lot of attention into the specific compression number as long as they are fairly even. You can see a difference of 5-10psi on the same cylinder depending on temps, method of checking, motor temp, when the last time the ski was ran, oil in the cylinders etc etc etc etc......
Personally, I start to worry when I see a difference of about 10% between the 3 and usually when there is problem it's pretty obvious.... like 112-70-115
Good luck with the new ski.
05-23-2010, 10:37 AM #9
05-26-2010, 06:08 PM #10
Cheers boys... I ended up picking up a pretty immaculate 02 1200 with 71hrs. Comp was spot 120 on all three so i pretty much jumped at it. Although when i looked at the ski an done the test also for myself i noticed they had BR8ES plugs an so changed to the recommended plug & now runs like a clock
Have sealed the pump shoe up & done the plate & grate to start it off...
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