Identical Bikes (one runs soft and very cool)

[snowbikethings]

I have two identical 2015 450sx snow bikes both with thermostats that had to have replacement elements. Both were rebuilt by same shop, both have Vortex ecu's one has a users on hill map one has standard mapping.

One bike with the on hill tuning runs a lot softer on bottom end then the other one. Up high it's a bit fluffly and doesn't rev out as good. It also really really struggles to build temperature. It can idle for 10 minutes and not even over heat. (thermostat element was verified) temperature gauge was verified.

I haven't swapped ecu's yet to verify it's the tune, but what part of tuning/fuel injection would run a bike very cold. We can get it to overheat if we try really hard in the trees.
Cam chain is new valve seats were re-ground.

Is it timing, leaking valve, too rich too lean. What tuning factor causes a bike to run cold and loose torque/over-rev.

 

[dooman92]

snowbikethings, you could have two separate issues, the cold running may not be, or very little, impacted by the tune. the thermostat has very little affect on engine temp if the rads are cold. If the rad stays cold the cold coolant falls into the engine case via the lower rad hoses. You will never get the engine warm with a cold rad. Warm coolant rises and cold coolant falls in the same hose. A cold rad has more heat shedding potential than the engine can produce. Rads have to be completely covered in deep powder in order to protect the rad from the heat sucking snow. Lean generally runs warmer and richer cooler, but the cooling system has more impact than the tune in my experience.

 

[snowbikethings]

snowbikethings, you could have two separate issues, the cold running may not be, or very little, impacted by the tune. the thermostat has very little affect on engine temp if the rads are cold. If the rad stays cold the cold coolant falls into the engine case via the lower rad hoses. You will never get the engine warm with a cold rad. Warm coolant rises and cold coolant falls in the same hose. A cold rad has more heat shedding potential than the engine can produce. Rads have to be completely covered in deep powder in order to protect the rad from the heat sucking snow. Lean generally runs warmer and richer cooler, but the cooling system has more impact than the tune in my experience.

My only concern is that when idling one will warm up very quickly the other wont warm up almost at all. Thermostat elements were both replaced, I wonder if maybe the aftermarket radiators are somehow cooling it through convection like you said with the extra aluminum on the radiators. I wouldnt think it would make that much difference hmm.

 

[eric82930]

If your engine is running clean enough to fire on every stroke the temperatures won't be that much different between them idling. Something must be wrong in your thermostat or plumbing. Defective new thermostats are pretty common in these days. Once it's running if it's not getting up to temperature then yes it will be slow because of the choke mode of the ECU

 

[dooman92]

Many things too consider. Do they both have the same convection route so it is a straight fall into case. Any bend will act like a trap and slow convection cooling. Different rads could very well do a better job of dissipating heat. Does the thermostat have a bypass? Both the same? Bypass on thermobob provides a lot of cooling potential. We found in early emission systems on autos that retarded timing resulted in faster engine warmup. The rational was slower longer burn gave up more heat to the block and coolant. We lost power (heat energy) compared to more advanced timing but it reduced nox emissions. Over advanced timing could steal a little heat but that should show in detonation if that is the problem. And timing has much less impact than your cooling setup. I would be examining my plumbing, thermostat bypass, and limiting the convection by covering and allowing rad to warm up. Let us know if you make progress.

 

[snowbikethings]

Thanks for the information, this is the kind of info I seek. Yeah I build identical builds in every way shape and form. Same Tstats just slightly different ecu tune same boxes etc. Both had fuel pumps and full engine rebuilds same time. Similar hours. The one that's colder does have a chinesium rad that's fabricated out of aluminum, like you said I wonder if that radiator pulls way more heat out of the bike. The retarded timing thing is great information that it warms the bike up.

 

[dooman92]

On deep powder days an exposed rad will not get warm and the bike will never warm up. The worst setups are where the rad and hose is directly above the engine coolant entry point, KTM style. My 2010 Husky was setup with far less convection cooling and it had very consistant temps. On my ktms if I didn't block off rads in powder I would never see over 100F. Cover up the rads with a cloth that severely limits snow and air flow intrusion and test. Take a ride covered and then uncovered. When the rad is cold the thermostat will be shut and all heat is lost via convection not circulation through the stat. When the rads get warm now cooling can be regulated via the thermostat.

 

[needpowder]

My only concern is that when idling one will warm up very quickly the other wont warm up almost at all. Thermostat elements were both replaced, I wonder if maybe the aftermarket radiators are somehow cooling it through convection like you said with the extra aluminum on the radiators. I wouldnt think it would make that much difference hmm.

I think you have a bad thermostat but maybe not. Also, it’s real easy to just swap the ECU’s at least it is on my Yamaha’s. I’m not super familiar with where the KTM one is located. Doubt that is it but it’s something to rule out. Then you can just fire them up in your garage and see what happens before and after. also pretty easy to swap thermostats. Good luck. Definitely cover your radiators in cold powder. what I use and have seen the most is a thin strip of whatever even a beer box in a pinch that you can slide in and pull out on the trail if it gets hot.

 

[byeatts]

On deep powder days an exposed rad will not get warm and the bike will never warm up. The worst setups are where the rad and hose is directly above the engine coolant entry point, KTM style. My 2010 Husky was setup with far less convection cooling and it had very consistant temps. On my ktms if I didn't block off rads in powder I would never see over 100F. Cover up the rads with a cloth that severely limits snow and air flow intrusion and test. Take a ride covered and then uncovered. When the rad is cold the thermostat will be shut and all heat is lost via convection not circulation through the stat. When the rads get warm now cooling can be regulated via the thermostat.

Hmm My KTMs run 160 -190 all day in over the fender powder., I use rev up covers and a cabon block off plate that seals off the front of engine fully aroung the pipe . It not a problem with KTM, FYI the Seklirk system adds over 20 lbs weight with coolant and does the same thing to hold temps up. , Riding on snow is all about the weight and no two engines are identicle , The machining process on every part manufactured will vary depending on the calibration of tooling and how many parts have been machined.