Hardcore Sledder banner
1 - 20 of 36 Posts

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #1 ·
well took my project out today with a motor that was claimed to have 1100 miles on it and it had okay low end torque and snappyness, but it wouldnt pull even stock weight for a zr. it would only pull 67g of weight to get it to 7700 RPM's. i know this sled should definately be able to pull more weight.

i checked compression and in one cylinder it had 122 PSI and the other 124 PSI. im pissed now cuz the guy said it was a motor with 1100 miles and no motor with that few miles should have compression. i would think it should be around 140 or so. no less than 135.

does this sound like a top end rebuild? what does that consist of and how much is that going to cost me. ive spent alot of $$ on this and expected it to run flawless not a shit motor.
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #2 ·

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #5 ·
SLP pipe, and they call for 7600-7900 so i am not over. how do i check valves are working, the motor runs its cycle at start-up once. 25/41 gearing. clutches have been aligned, but never been serviced. was told 1100 miles on them.
 

·
Registered
Joined
·
371 Posts
SLP pipe, and they call for 7600-7900 so i am not over. how do i check valves are working, the motor runs its cycle at start-up once. 25/41 gearing. clutches have been aligned, but never been serviced. was told 1100 miles on them.[/b]
Good way to make sure power valves are fully opening and at the same time, is to take off exhaust y-pipe so you can put your fingers up in the ports to feel the valves. Next take the apv cover off the servo motor and use a adjustable to cycle the servo to the fully open position and then feel if the valves in the ports are fully open. If they aren't adjust cables till both valves open at the same time and together. I was amazed when i did mine as they were set to manual spec and not the misprint measurement either, mine were not even close as my cables had stretched. Anyway hope this helps :div20:
 

·
Premium Member
Joined
·
1,873 Posts
Months ago when you started this project I recomended that you take the engine apart and get the crank trued and welded. Every 900 engine that I have worked on is out of spec.
The 800 engine holds up a lot better, although the same crank.
I know for a fact that the 900 engine in my Frankenstein had a 1000 miles on it.
My crank was way out of whack upon inspection of dis-assembly.

I am running a D&D single pipe and can on mine with a Cat orange/ white primary spring and 76 gram weights running 7700 rpm.

I am leaning toward your crank being out of phase.

My 900 that I had a few years ago wouldn't rpm either, I took a total of 10 grams out of the primary and it still wouldn't rev
over 6800 rpm.
What happens is that the engine is so far out of alignment, that it has a "tug of war" so to speak against the harmonics.

If you take something that rotates and it is 2 grams out of balance, spin it 8000 rpm, that 2 grams turns into 80 lbs of rotating force fighting against itself = Bad harmonics beating the piss out of itself until it breaks.
 

·
Premium Member
Joined
·
2,611 Posts
124 is low for a 900...should be around 145-150,my 03 had 152 hot on both sides.get a quality gauge and check it again :div20: if it was a power valve issue i dont think it would turn up 7700rpm.
 

·
Premium Member
Joined
·
12,762 Posts
Months ago when you started this project I recomended that you take the engine apart and get the crank trued and welded. Every 900 engine that I have worked on is out of spec.
The 800 engine holds up a lot better, although the same crank.
I know for a fact that the 900 engine in my Frankenstein had a 1000 miles on it.
My crank was way out of whack upon inspection of dis-assembly.

I am running a D&D single pipe and can on mine with a Cat orange/ white primary spring and 76 gram weights running 7700 rpm.

I am leaning toward your crank being out of phase.

My 900 that I had a few years ago wouldn't rpm either, I took a total of 10 grams out of the primary and it still wouldn't rev
over 6800 rpm.
What happens is that the engine is so far out of alignment, that it has a "tug of war" so to speak against the harmonics.

If you take something that rotates and it is 2 grams out of balance, spin it 8000 rpm, that 2 grams turns into 80 lbs of rotating force fighting against itself = Bad harmonics beating the piss out of itself until it breaks.[/b]
In light of what I've seen this fall on two 900 cranks (my own and Sleddogs) IMHO that was good advice. Tie the valves in the open position with the servo disconnected .................now run it and see if your top end returns.
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #10 ·
how do i tie the valves in the open position? i will try that first. the guy i got the motor from, (catpunk) bought it from speedwerx1000 on here, and catpunk said he would get the crank welded for me since he was getting his done. do the crank should be welded. first i will try the valves in the open position.

but i really hope its not the crank. anyway to check if it is the crank without taking the whole motor apart which i just put in....
 

·
Premium Member
Joined
·
1,873 Posts
You pop the clutch off and get a dial indicator and put it on the end of the crank sticking out of the engine.
You must make sure that the indicator is on the engine somehow
I have taken the reed cages out and bolted a piece of steel to it and used a indicator with a magnetic base.
Pull the plugs out and have someone turn it over slowly with the pull rope.
Spec is .0015 to .002 thousandths runout.

All the ones I have done were always out more on the mag side.

I would bet you a beer that your is out .005 or worse
The crank on mine was out .008 on the pto and .014 on the mag, the center section of the crank was pulling apart and started rubbing on the case.
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #13 ·
what kind of stores will have the dial indicator i am looking for? this really sucks, its snowing hard here and minimum 5" on the ground.

roughly how long does it take to pull the motor apart and get the crank out, i will be having a buddy help me and he knows his stuff.
 

·
Registered
Joined
·
371 Posts
You pop the clutch off and get a dial indicator and put it on the end of the crank sticking out of the engine.
You must make sure that the indicator is on the engine somehow
I have taken the reed cages out and bolted a piece of steel to it and used a indicator with a magnetic base.
Pull the plugs out and have someone turn it over slowly with the pull rope.
Spec is .0015 to .002 thousandths runout.

All the ones I have done were always out more on the mag side.

I would bet you a beer that your is out .005 or worse
The crank on mine was out .008 on the pto and .014 on the mag, the center section of the crank was pulling apart and started rubbing on the case.[/b]
SHIT!!!.....I see what I'm going to be doing for the next little while, the same thing your going to be doing by the sounds of it. My crank is way outta spec and it has only 1500 miles on the motor. Good luck and may the force be with you LOL. :div20:
 

·
Premium Member
Joined
·
1,873 Posts
I have a buddy that is a machinist and I have always borrowed his.
You could get a cheap one from here

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=93051

You will have to completely dis assemble the entire engine to get the crank out of it.

I have done a lot of them, it will take me about two hours to take the engine out and taken apart
and about 3 hours to put it back together and get it back in.
John at
www.northerncrankshaft.com
can true and weld it for you for around a $150 plus shipping
Send it in the case with a few bolts in it to make sure the bearing pins are in the right place.
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #16 ·
I have a buddy that is a machinist and I have always borrowed his.
You could get a cheap one from here

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=93051

You will have to completely dis assemble the entire engine to get the crank out of it.

I have done a lot of them, it will take me about two hours to take the engine out and taken apart
and about 3 hours to put it back together and get it back in.
John at
www.northerncrankshaft.com
can true and weld it for you for around a $150 plus shipping
Send it in the case with a few bolts in it to make sure the bearing pins are in the right place.[/b]
the guy i bought the motor from said it was just welded and trued before he sent it to me. i can see that it recently was taken apart because there is orange sealant around the case. my buddy said its a compression issue. if its at 120 now and new it was 150, thats a 20% decrease in power, and i guess that since it wont pull 74grams and only the 67-68 grams, thats sounds about right, thats 15-20% less weight. and it would pull 7000 RPM with the 74-76 grams in it, and with 67-68 it would pull 77-7800. im ordering new rings for it, and maybe pistons upon inspection if they need to be replaced. but in the mean time i am going to ask around for a dial indicator. i know the owner of FAST so i am stopping by there tuesday to see if they have one, and what they think the problem could be, and if i cant use the gauge if they can check it.
 

·
Registered
Joined
·
642 Posts
I'm going to throw my 2 cents in.

You definiately should try another compression gauge before tearing into the motor, comp. should be 140-150. I just checked an 03 ZR9 with 2800 miles, 150 in both holes. Also, check the runout but you say it's been fixed so here goes...

I have a 02 ZR800 with Black Magic Super Single, port, reeds, airbox mods, Tempaflow, trued and welded crank. When stock, I was running 74-75 gram Heavy Hitters with a 62/50 Helix at 7200-7300 on digital tach. After I did the port and BM Single, I had to make DRASTIC clutch changes to acheived desired RPM of 77-7900. Weights are now at approx. 70 grams with a 56/38 helix and RPMs pull to 7700 and climb to 7950. Going from a 62/50 to 56/38 is a huge change but that's what it took to get my RPM's up as well as taking out 4-5 grams of weight. I also went through a similar situation with my bud's sled, a 03 ZR900 with Speedwerx single.

So what I'm saying is it normal to drop alot of weight to reach desired RPM's with aftermarket pipes. Think my sled must be slower now than stock because of less weight and shallower helix? In trail mode, stock was 101 in 1000'. Now 106 in 1000'.

BTW don't compare loss of comp. to loss of weight, really doesn't work that way. Good luck.

APVZR8
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #18 ·
well tried 2 other gauges, and they averaged 123lbs of compression in each. the crank has been welded and trued by straight up performance. i'll check for air leaks around the reed cages by spraying ether around the carb boots and whatnot.

guys with SLP pipes on their stock 900 motor said 76g is easily possible with it.

right now it has trouble pulling 67 to pull rpm's. it feels as it the motor is having trouble/lugged down, which leads me to compression for high end horsepower. i'll go through the clutches again. but its either the clutches or compression not pulling the weights up high.
 

·
Registered
Joined
·
4,990 Posts
Discussion Starter · #20 ·
i just checked my c-c for the heck of it, and guess what, its 11.25 when the belt is for 11.5". does anyone know of a cat or poo belt that has a 11.25" c-c distance?
 
1 - 20 of 36 Posts
Top