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600 CFI2 not revving over 7900

Maydaze

Maydaze

New Member
Messages
20
Age
57
Location
Hagaman, New York
Country
USA
Years Snowmobiling
48
Snowmobile
Polaris Assault 800
Ok, this is my second IQ chassis 600CFI motor that will not rev over 7900. 8000 on a long lake. The first was a 07' 600CFI 4 injector now this is a 09' 600CFI 2 injector. The sleds ran strong....8250-8300 all day long. Then it was like you flipped a switch....7900. Instantly. I had the 07' at a dealer for a week and they could not find the issue. Sold it. It is not clutching, it is not the power valves....it is an electronic issue or fuel related. The sled runs great, no bog, no backfiring, plugs are actually black, not running lean. It acts like the timing is retarded and not letting it rev. No warning lights, nothing. There are so many of these small block CFI sleds with the same issue and not one fix anywhere on the web. So many items feed info to the ECU....exhaust sensor, DET sensor, TPS sensor, Water temp sensor, Map sensor, Crank sensor (2), stator, capasitor, regulator....somebody has had this issue and corrected it....what is it?
 
Did you do a compression test?
 
....sorry, should have given more information. The top end was done around 1500 miles ago....120+ on both sides. The sled runs regularly between 125 to 135 degrees. On low snow conditions it may get up to high 140's, rarely 150. I replaced the exh. pipe sensor about 2 or 3 years ago, but it was giving a code for that. I have had this sled since it had 400 miles on it. It now has just over 5000, but the top end only has 1500 miles. It has run like a fine watch until this year. I am going to check the resistance/ohm reading on everything that I possibly can. I have 2 dealers close by that I trust to hook up to Polaris' Digital Wrench, but I know there is only so much it can tell you. Frustrating.....
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Covering the simple things here first. Since you said it ran great all along to 8200 and all of a sudden dropped to 7900. Did you happen to change anything in your clutching or have them cleaned this year? I'm thinking possible for the primary spring to be wrong or possibly it's broke on one end of the spring. This would still allow the sled to engage fine but would not allow top rpm. Sometimes if they break on one end, you will not notice until the clutch is apart.
 
You can have breakfast on my clutches and lunch on the valves....spotless. New primary spring (2 weeks old), clutch weight bushings tight, new secondary clutch assy. (took off P2 put on new take off Team), new belt (old belt spins same rpm's), new plugs, fuel filter one year old....the motor is definitely retarding the timing and adding fuel. The plugs are black. I will be testing all the ohm readings on all the sensors. So fare the T-map sensor checks out fine, water temp sensor fine, exhaust sensor is slightly lower on the ohm reading than the brand new one I have but not alot. I will be checking the capasitor, regulator ac/dc, regulator dc voltage booster and TPS sensor tonight. It is hard to get a timing light over the opening on the case to check the timing, but I am going to try that also.
 
Just a guess but, could be drag. Wore hy-fax or track. I had a the bolt break that holds the hy-fax in place, and at speed the hy-fax would work it's way out, and when you slowed in would return to the proper set. Drove me nuts trying to find that problem.
 
Well, i've replaced the water temp sensor, exhaust sensor, knock sensor and MAP sensor in the air box. The sled rev's 7950-8000 max. Rolling resistance is minimal. You can turn the track with one hand easily. Emailed Polaris and they gave me a case number. Poo told me to bring it to one of my local dealers and have them plug it in to the Digital Wrench and then have them call Poo. Unfortunately we lost all of our snow here and it is impossible to test it out. I have been doing hill climbs with my son on weekends that they are running here in NY and that is my only test session. This winter sucks.
 
Have you whacked throttle on Jack stand to see if it will rev over 8000?
 
Brock, yes I had it on the stand and just gave the brake lever some light pressure so the track would not balloon.....8k max.
 
Check your exhaust valves ,bellows, and springs. Disconnect e/v solenoid hoses and plug nipples run on stand.
 
Check resistance and continuity on everything and wiring .
 
Loren Ward said:
Check your exhaust valves ,bellows, and springs. Disconnect e/v solenoid hoses and plug nipples run on stand.
Click to expand...

Did all of that.....lets put it this way......I have checked, cleaned, replaced everything except the ECU, Injectors, Fuel pump and Stator. I am going to check more of the wiring like Brock said. It amazes me that there are literally case after case of this issue with the 600 CFI motors on the web and not one case of a definite repair or cure. My 07' did this, my friends 11' just had this happen this year, my 09' this year......and mileage does not matter. The 07' at 3100, the 11' at 2100 and the 09' at 3900 miles. The sled is cherry, that is why I am putting so much effort into a cure. I've checked the compression cold (120+) but never hot. Another test. I wish I had an EGT gage to check how it is burning at WOT (has to be rich/cold as the plugs are black). Is there a way to take the wiring from the Exhaust temp sensor on the pipe and tap into the plugs to run an actual temp gage?
 
It isn't as common as you may think. I don't have any around here doing what your describing in any 600. These are the ones running strong. It's usually the 800 with some problems.

If you have a dyno to go to that has a digital wrench too. This would tell you everything you need to know.

It can monitor everything from bsfa, afr,cfm, exhaust temp,coolant, resistance,continuity,intake temp,etc......
This would tell you what's going on for around $200.00. To me that's money well spent. Just an observation.
 
Maydaze, it sounds like you have covered all your bases. I know you said you checked the exhaust valves and they were clean. Are you sure the holes going into the cylinder are clear? A quick check is to pull the spark plugs and exhaust valves. Spray a small amount of carb cleaner in the holes. Look into each cylinder and see if the cleaner is making it into the cylinder. another quick check on the valves is to depress the valve into the housing and block the hole with your finger. I don't know if your application uses an exhaust solenoid, but if it does, block that port also. Release the valve. It should only come out halfway and stay there indefinitely or until you release your finger from the vacuum port (ports).

Hope this helps.
 
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Stormrider3 said:
I had a sled with similar symptoms it turned out to be damaged reed petals.
Click to expand...

I am new to the reed scene. Does anyone think that the aftermarket reeds are beret than the oem ones and which ones to buy? I have an 09 SBD 600
 
We've seen this happen many times with regulator problems and stator. Regulator is the most common. It goes into a safe mode and won't let the sled rpm where it is supposed to.
 
Regulator is new. The only items not replaced are the stator and the ECU. Every sensor that can be changed has, injectors checked and cleaned, compression is 119 and 120, reeds replaced......so stator or ECU are it.
 
Have you changed the fuel pickup shock in the tank? I had one that was totally plugged but showed good fuel pressure on a stand
 
Well after exhausting all my options, I tried something I did not think about. I checked the compression when hot. 115 and 118 in the cylinders. I pulled the top end off and saw some fine lines on the PTO piston running vertical on the exhaust side. I had a PTO seal weeping a year or two ago and had it replaced.....this may have been the issue on the piston. I honed both cylinders and put in a new set of Wiseco pistons ( i have had great luck with Wiseco over the years, no issues ). Let her break in and 'BAM'.....8300-8400 rpms!! Back to running like an animal. I put in some 66 gram weights to keep it under 8350 rpms. I actually did this last year and never posted that it was fixed. Who would have thought.
 
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