Setting off DET sensor on 600ho

[champyfz450]

I have a 600ho carb in a Iqr chassis and cant keep the thing from tripping the DET sensor. Ive tried just about everything but the only thing that will make it go away is to run a gallon or so of race fuel for every tank. The only thing left that I havent tried is to adjust the timing and to be honest I dont really know how. Any help at all guys would be greatly appreciated. Thanks

 

[sled_guy]

What other mods are done to the motor? What pipe are you running? Stock head?

sled_guy

 

[champyfz450]

The only motor mod is a neils custom pipe made for this motor in this chassis. The head from what I know is stock. I dont know if the timing was advanced to 28* like a lot of guys with that motor were doing. The piston wash looks great from what i can see so Im starting to wonder if Im getting some sort of vibrations or something causing the DET to trip. Im all outta ideas!

 

[sled_guy]

If you were getting vibrations then the added race fuel wouldn't stop it. For sure vibrating exhaust springs can trip the DET, but if you put a gallon of race gas in it and it stopped then you have timing/pipe/compression issues.

I assume that running a gallon of race gas isn't what you want to do? Check the squish... it wouldn't be the first time that a factory head came really tight. I saw it on an '02 700 motor, squish was so tight that anything below 5000' and in stock trim it would have det issues.

I'm not familiar with the neils pipe, but these 600 motors are typically pretty dang forgiving. I did see one last year that had the head cut a little and started having det issues so that's why I'm suggesting you check the squish.

sled_guy

 

[champyfz450]

Thanks very much for the help. Could you please point me in the right direction on how to check the squish. Im very mechanically inclined but Ive never dealt with sleds up until last year. As far as the pipe goes the builder of the pipe(NPP) assures me that its not the pipe. He has built a lot of pipes for the 600ho in the iq racer chassis. If the squish is fine I guess it just comes down to the timing! Again thank you very much for your help so far

 

[MNSLEDNECK56308]

I had the same sled, same motor, same exhaust exhaust. And never once saw the DET. What size mains you running? and what elevation? Did you maybe get a 600HO mod motor?

 

[sled_guy]

Take out the spark plugs. Bend 2 pieces of solder and insert in to the spark plug holes and extending all the way out to the side of the cylinders. Turn the clutch so that the piston comes up and smashes the solder flat, make sure and rotate the motor past top dead center. It will smash the solder out flat. Then remove the solder and mic.

You have to get the end of the piece of solder all the way out to the edge of the cylinder so that you get a measurement on the squish.

sled_guy

 

[champyfz450]

I had the same sled, same motor, same exhaust exhaust. And never once saw the DET. What size mains you running? and what elevation? Did you maybe get a 600HO mod motor?

Im running 390 mains at approx. 1300'. Mine sets off the DET absolutely everytime! The motor came out of an 07 fusion with 700 miles from what I was told.

Thanks sled_guy for the advice and I will check that tonight. Do you or anyone know what the squish is supposed to be and if its too tight can it be easily fixed with an extra head gasket?

 

[MNSLEDNECK56308]

Boy, that is weird. Like Sled said it must be a timing issue. But your 390's sound fine. Only thing i can think of, do you have the "choke" in the pipe from Neils? Was the exhaust for a 800 not a 600, could be a flow issue. Not sure if that would set off the DET or not! Just throwing out ideas!

 

[champyfz450]

Boy, that is weird. Like Sled said it must be a timing issue. But your 390's sound fine. Only thing i can think of, do you have the "choke" in the pipe from Neils? Was the exhaust for a 800 not a 600, could be a flow issue. Not sure if that would set off the DET or not! Just throwing out ideas!

Yup got the choke in. I even called neil to send me out another one to try just in case the one I had was the wrong one. I guess ill have to learn how to check the timing and give that a shot too. couldnt hurt right? At the end of my rope here guys, all outta ideas.

 

[MNSLEDNECK56308]

well its either timing or perhaps a wiring issue with the DET sensor.

 

[craze1cars]

When you say you've tried everything...what exactly have you tried except more octane?

Hate to be "Mr obvious" here...but have you actually tested the DET sensor? According to my Poo service manual the knock sensor has a spec of 4,870,000 ohms.

Or just put a new one in if you want to try throwing parts at the problem...cost less than $50 from the dealer.

Otherwise, here's Poo's breakdown from the service manual on how to prevent detonation...I realize this is a mod sled, and most of us don't operate "by the book", but maybe their list will help remind you to check on something you haven't checked yet.

Always use premium fuel
Follow carb jetting guidelines
do not modify engine/exhaust system with non-approved Polaris mods
Verify there is no water or foreign material in fuel
Verify no internal engine damage
Verify the cooling system is working properly.

I presume you've also looked carefully for air leaks? Crank seals, carb boots, manifolds, etc...DET is often kicked off by a lean condition. You could also try bigger mains just for fun and see if the problem goes away.

And you really do need to check your timing...

From your description, it sounds like you are not the person who built this sled...did you buy it used? If so, it's quite you don't really know what you have in terms of mods. This motor might not be set up to run on pump gas at all...

 

[craze1cars]

Also from Poo service manual:

IGNITION TIMING
Timing Procedure - Carbureted Engines
NOTE: Always verify timing of engine at room temperature (68°F / 20°C), and at the specified RPM. If applicable, make sure the key switch is in the PREMIUM mode and the TPS is unplugged.

1.Reference the timing specification chart.

2.Install a dial indicator gauge into the MAG spark plug hole.

3.Place the MAG piston in the proper timing position, then mark the flywheel at this point.
EXAMPLE: 600 HO Carbureted = 26° @ 3500RPM. Place the MAG piston 4.0096mm (0.1579in.) BTDC.
NOTE: Each 10 degree mark is separated by lines every 2 degrees (not shown). Acceptable timing variance is +/- 2 degrees.

4.Connect an accurate tachometer and a good quality timing light to the engine according to manufacturer's instructions.

5.Disconnect the throttle position sensor (TPS), if equipped.

6.Start engine and increase RPM to the point specified in the timing specifications. Hold the throttle to maintain specified timing RPM.

7.Point the timing light at the timing inspection hole.

8.With your head positioned so there is a straight line between your eye, the stationary pointer and the crankshaft center line, note the relative position between the marked flywheel line and the pointer. If the stationary pointer is aligned with the mark made in Step 3, or within the acceptable variance, ignition timing is correct.

9.If the pointer is outside the variance, the stator will have to be rotated either with crankshaft rotation (to retard the timing) or against rotation to advance it. NOTE: Rotate stator plate approximately the same distance as the marks must move. In most cases, the recoil starter housing, recoil drive hub, and flywheel must be removed to loosen the stator bolts and change the timing. On some engines, the stator plate
retaining screws can be accessed through the flywheel.

10.Torque stator plate screws and flywheel nut to specified torque. Apply Loctite 262 (red) to crankshaft flywheel taper if required. Refer to the Specifications section for torque specifications and flywheel installation procedure for engine type.

 

[champyfz450]

When you say you've tried everything...what exactly have you tried except more octane?

Hate to be "Mr obvious" here...but have you actually tested the DET sensor? According to my Poo service manual the knock sensor has a spec of 4,870,000 ohms.

Or just put a new one in if you want to try throwing parts at the problem...cost less than $50 from the dealer.

Otherwise, here's Poo's breakdown from the service manual on how to prevent detonation...I realize this is a mod sled, and most of us don't operate "by the book", but maybe their list will help remind you to check on something you haven't checked yet.

Always use premium fuel
Follow carb jetting guidelines
do not modify engine/exhaust system with non-approved Polaris mods
Verify there is no water or foreign material in fuel
Verify no internal engine damage
Verify the cooling system is working properly.

I presume you've also looked carefully for air leaks? Crank seals, carb boots, manifolds, etc...DET is often kicked off by a lean condition. You could also try bigger mains just for fun and see if the problem goes away.

And you really do need to check your timing...

From your description, it sounds like you are not the person who built this sled...did you buy it used? If so, it's quite you don't really know what you have in terms of mods. This motor might not be set up to run on pump gas at all...

No Im not the one who built this sled. The dealer that I bought it from installed the engine and told me it was a bone stock motor. I checked everything in the cooling system, put a new sensor in, have tried the sled up to 420 mains, tried a stock 600rr pipe and can, only thing i havent tried yet is checking the timing. I forgot to mention that there are vforce reeds in it also and I just put in the spacer kit to clear the impulse line port. Thanks a lot for the help guys

 

[sled_guy]

To change the squish you have to machine it... the heads are o-ring heads so putting a spacer in isn't an option. Some guys have tried an extra base gasket, but that changes port timing and the 600 motor has a little bit of an issue with the water jacket sealing at the bottom of the cylinder anyway so putting a second base gasket there isn't going to make that any better.

I'm not sure on the stock motor, but the rule of thumb I've always used is anything under .060" is too tight.

sled_guy

 

[champyfz450]

Thanks you very much sled_guy youve been a lot of help. Ill check the squish tonight

 

[AKSNOWRIDER]

champ, my buddies edge 800 will get det light below 3000ft. with race twins on..stingers are to small....might be what you are seeing...

 

[champyfz450]

champ, my buddies edge 800 will get det light below 3000ft. with race twins on..stingers are to small....might be what you are seeing...

The pipe that is on this engine has a removeable aluminum "choke" in it. Maybe I could ask the pipe builder for a larger choke to see if that fixes it. Afterall I am riding between 800'-1300'. Although when I had the sled in Valemount BC it would happen on long WOT runs uphill at 6500' or so.

 

[Rick!]

champ, my buddies edge 800 will get det light below 3000ft. with race twins on..stingers are to small....might be what you are seeing...

I'm kinda thinking the same thing. My 06 HO would DET after a 1/2mile WOT at low elevation with anywhere from 390 to 420's. At high elevation, it would not DET at -15 WOT with 280's at 8000 feet. It also had V-Force reeds and SLP pipe/can. I'd remove the "choke" and retest the DET thing. Other obscure vibration/noise sources are a crank that is a tad close to the case on the MAG side and the pork chop makes contact. You also said you installed the reed spacers. Have you ran it with them? Running out of fuel is a real good way of creating DET. The one good thing out of all of this is that you are not hurting the engine. Non-DET engines would probably have a few piston issues by now with the amount of light activation you are experiencing.

The last "duh" thing to check is the fuel tank venting. Maybe take the gas cap off and retest and see if things are better.

 

[champyfz450]

I'm kinda thinking the same thing. My 06 HO would DET after a 1/2mile WOT at low elevation with anywhere from 390 to 420's. At high elevation, it would not DET at -15 WOT with 280's at 8000 feet. It also had V-Force reeds and SLP pipe/can. I'd remove the "choke" and retest the DET thing. Other obscure vibration/noise sources are a crank that is a tad close to the case on the MAG side and the pork chop makes contact. You also said you installed the reed spacers. Have you ran it with them? Running out of fuel is a real good way of creating DET. The one good thing out of all of this is that you are not hurting the engine. Non-DET engines would probably have a few piston issues by now with the amount of light activation you are experiencing.

The last "duh" thing to check is the fuel tank venting. Maybe take the gas cap off and retest and see if things are better.

Ive considered the vibrations and the tank being airlocked but I ruled those out when I used a little race gas and it completely went away. Like I said, the det kicks in everytime I ride it without race gas and never kicks in when I do use it. Thats why I keep coming back to the timing being off or the squish being too tight. I dont have a two stroke timing light so Im gonna bring it to my local dealer on saturday and have him check the timing.