Need HELP please!!! Ready to burn P.O.S!!!

[Go-Vertical]

03 polaris 800 rmk power/rmp drop @ wot 7500-7600.Ok at at 3/4 trottle 8100. Temps drop on both cylinders. Things I have done and checked are:
New eng complete comp- 125psi on both cyl.
tps sensor replaced and set
cdi replaced
stator replaced
carbs gone through
coil replaced
reeds did visual inspection good
checked base timing good
ves valves cleaned and bellows replaced
clutches rebuilt
plugs replaced even closed gap to lighten load on secondary ignition system
wiring all good (checked resistances) and grounds disconnected all kill switches
temp sensor tests normal
put stock exaust back on
fuel pump tore down and inspected,checked vac pulse line seems ok
Checked fuel restictions from tank to pump Intank sceen inc.
Tried cdi from 700 rmk run ok little lower on power ( Less timing advane on the 700 than the 800)
any ideas would be greatly appreciated

 

[Nytroman]

Sounds like it is running smooth, just dropping temps and rpm at over 3/4 throttle. I am assuming you have played with the main jets which control 3/4 to full throttle. I also I had an '02 and aways run great. I piped it and did some jetting on it so to be safe i ran premium and the thing would not pull over 7800rpm. I messed with the jetting and clutching all day. Next day said pi$$ on it and put in regular and it ran top notch again. Seen it again on a quad this summer, would'nt run on premium/AV mix, put in reg and would run great. Not sure of all your circumstances but a cheap try.

 

[DRD]

Does it surge at WOT or just drop and maintain the lower RPM?

 

[Garryese]

... and what is the cylinder temp change? Where is the temp taken from?

I am guessing either a fat main jet/lean needle setting combination or reed flutter.

 

[thump]

Gathering from your info,,,,,I would drop main jet 2 sizes and watch cyl temps at WOT to see a temp change on your Digitron. If this does help,,you may have to lift the needles a notch as the midrange will also lean out with the jet change.

 

[scotts]

May be a clutching related issue if you say power power and rpm drop. are your clutches binding as it aproaches shift out????

 

[Go-Vertical]

Does it surge at WOT or just drop and maintain the lower RPM?

surge at wot temps drop from 1150 to 850 tried leaner and richer fuel mixtures no real difference. rebuilt primary and stock secondary new hcx roller secondary also.

 

[DRD]

My 800 Rev was doing the exact same thing. It turned out to be a thing called "pipe surge". I can't say if Polaris twins will do it or not as I'm not that familair with them. At any rate it turned out that loading the motor a little more allowed the pipe to build heat the way it should and the problem went away.
One other thing I found on a Polaris twin was once was that the VES had the threads stripped on the end of the valve and it would only grab once and a while and and open.

 

[Garryese]

surge at wot temps drop from 1150 to 850 tried leaner and richer fuel mixtures no real difference. rebuilt primary and stock secondary new hcx roller secondary also.

If it was clutching you would not see that type of temp drop.

I'd go back and have a much better look at the reeds.

 

[maxwell]

this is pipe surge.

load the motor. try a stiffer primary spring



here is DJS explaination



Not enough flyweight will reveal pipe surge "the zoomies" where with engines that have higher compressions of around over 145 lbs, you'll never see correct rpms, only see low rpms from - pipe surge!

Some people will know the sound of "rah rah" or some people call it the "Rah rahs" You press the throttle to the bar and the engine loses 3~400 rpms.
The throttle is pulled back to 3/4 and observe the rpms are back at 8000. Push the throttle to the bar again, observe 7700, let off the throttle, 8000. WTH???
- That is the zoomies "pipe surge" from lack of flyweight.

 

[cooper]

what he said.

 

[Go-Vertical]

this is pipe surge.

load the motor. try a stiffer primary spring



here is DJS explaination



Not enough flyweight will reveal pipe surge "the zoomies" where with engines that have higher compressions of around over 145 lbs, you'll never see correct rpms, only see low rpms from - pipe surge!

Some people will know the sound of "rah rah" or some people call it the "Rah rahs" You press the throttle to the bar and the engine loses 3~400 rpms.
The throttle is pulled back to 3/4 and observe the rpms are back at 8000. Push the throttle to the bar again, observe 7700, let off the throttle, 8000. WTH???
- That is the zoomies "pipe surge" from lack of flyweight.

stock pri spring is 120-340. running rcs ti I think the rate is 140- 350 How high should I go ? stock weights are 58 grams running 62 at altitude. should I try 64 at altitude maybe 66 here?

 

[DRD]

I think less spring will load the motor more, or try a heavier fly weight.

 

[SLEDBUNNYRACING]

Great ideas but I'd continue focus on the drop in RPM's and maybe relate it to pipe temp...that is where your power is at. On my 01 Poo I have adjustable jets and I can cool the pipe to 975 or raise them to over 1300 degrees (WOT) on the digitron with a couple of turns of the button and will drop 300 rpm real fast.
It sounds like it may be a fuel delivery problem as "thump" has suggested. You need to get here up to the 1200 + degree range.
What jets are you running or are you using an Atacc system?

 

[maxwell]

Great ideas but I'd continue focus on the drop in RPM's and maybe relate it to pipe temp...that is where your power is at. On my 01 Poo I have adjustable jets and I can cool the pipe to 975 or raise them to over 1300 degrees (WOT) on the digitron with a couple of turns of the button and will drop 300 rpm real fast.
It sounds like it may be a fuel delivery problem as "thump" has suggested. You need to get here up to the 1200 + degree range.
What jets are you running or are you using an Atacc system?

that is why he cant get his temps up enough. the motor is not being loaded enough.

you need heat in those pipes like mentioned in that range. load up on the weight a bit. try some different springs so your still keeping your correct max rpm with the extra weight. i cant really give you any weights or springs to sugest youll just have to try it out. (dont know the polaris clutching system well)

 

[Go-Vertical]

Great ideas but I'd continue focus on the drop in RPM's and maybe relate it to pipe temp...that is where your power is at. On my 01 Poo I have adjustable jets and I can cool the pipe to 975 or raise them to over 1300 degrees (WOT) on the digitron with a couple of turns of the button and will drop 300 rpm real fast.
It sounds like it may be a fuel delivery problem as "thump" has suggested. You need to get here up to the 1200 + degree range.
What jets are you running or are you using an Atacc system?

390 no altitude compensator here tried lower 350 here polaris calls for 410 at -10. I also thought about fuel pump issues was a pol bulletin about pulse line colapsing and the fuel pump relocation recall. This problem seems so strange run great before with 390 all the same set up just started doing this.Friend of mine also has 03 800 doing exactly the same thing.

 

[DRD]

When mine was doing it, I could see 1200f at midrange but as soon as I put the flipper to the bar, 850F. I looked the engine over pretty good before I read a thing on pipe surge, I never occured to me that such a weird condition could happen.

 

[SLEDBUNNYRACING]

I'm a bit at a loss on this one, seems you've more than covered off most of the possible problems, I'm guessing you've checked the carb boots for cracking as well?
It's gotta be something real simple that we've overlooked. I'd look at "maxwell's" suggestions and play with clutching. Play with the springs and weights a bit to load up the motor more.

Keep us informed, I'm very curious what you find?

390 no altitude compensator here tried lower 350 here polaris calls for 410 at -10. I also thought about fuel pump issues was a pol bulletin about pulse line colapsing and the fuel pump relocation recall. This problem seems so strange run great before with 390 all the same set up just started doing this.Friend of mine also has 03 800 doing exactly the same thing.

 

[thump]

Another shot in the dark,,you say in your original post you closed up the gap on your sparkys,, put them to spec and try.

 

[Go-Vertical]

Closed gap only to take some load off of the secondary ign. system. (Coil stator etc.) Trying weights tomorrow Finally days off.