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'20 TE300i stuck thermostat? Overheating badly...

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Background- bike has always ran a little hot, like most of them apparently. Installed a fan and that seemed to help a little but the fan was just always on then compared to my buddy's carb'ed TE300. I have the fan set to kick on at 190f. I just installed an RK Tek head and engine ice expecting it to run a lot cooler. I also turned the PV out 1/4 turn. All was well for about 15 miles and it started to overheat badly. Ended up pressure testing the system and found a real slight leak in two of the hoses at the clamps. Enough to lose enough coolant to make it overheat. Tightened everything up, pumped it up to nearly 2.0 bar and everything held. Went for a ride today and within 3 miles it was overheating again. Came home, checked everything again and all is tight. topped off the coolant with engine ice and rode around the neighborhood at 20mph and it would run all the way up to 190 when the fan would kick on. Doesn't seem right. It's 93F outside today but I still don't think it should run that hot when the bike is moving and it isn't under much load. 

I'm about to take it back to the dealer. The only thing I can think of is the thermostat isn't functioning and coolant isn't circulating. Anyone have any ideas? I've debated a thermostat bypass kit but I'm supposed to leave wednesday for a trip with some friends from out of state and the bike is currently not rideable. 

Edited by StreetDoctor

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Sounds like it’s running lean. Can’t be jetting, but maybe too much oil or not enough?

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5 minutes ago, 1 lunger said:

Sounds like it’s running lean. Can’t be jetting, but maybe too much oil or not enough?

I put a new plug in it before the ride today to see what it would look like but only put 5 miles on it total, not sure that's enough to really say? The electrode was definitely a little white. I uploaded a photo below. The bike is running perfectly though. No lean bog, no hanging idle, etc. When I swapped the head I looked at the cylinder walls and there was plenty of oil, piston had even burn marks. 

58845861089__54FF6E4F-500C-44DF-85C8-E507C43792DC.JPG

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don't top off radiator, drain it and measure the book spec back in (just over a qt), don't be surprised if it doesnt come up over the fins.  Don't trust the actual degrees shown if it's one of those between the fins probe's,  just tweek the fan on/off as you think it should be. Plug looks fine.   You didn't say if it was boiling?

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6 minutes ago, highmarker said:

don't top off radiator, drain it and measure the book spec back in (just over a qt), don't be surprised if it doesnt come up over the fins.  Don't trust the actual degrees shown if it's one of those between the fins probe's,  just tweek the fan on/off as you think it should be. Plug looks fine.   You didn't say if it was boiling?

It definitely boiled over the other day when I had the leak. It didn't boil over today so maybe it was just overfill but I have a between the fin's temp gauge for the fan and also a radiator cap gauge. They vary by about 20-30 degrees. The cap gauge was up to 250 with pretty mellow riding today. Way hotter than it's been in the past.  

Edited by StreetDoctor

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If you had hose leaks, it could have pulled air back in the system as it was cooling off. Then burped the next time you rode it.  But, ya I would expect the tpi to run hotter than a carb bike just because they are trying to meet euro emissions.

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It should warm up quickly. The whole purpose of a thermostat is to help the engine warm up quicker, rather than keep it cool. The thermostat sets the floor, not the ceiling. Any fuel injected engine needs to be at operating temperature to fun efficiently. Carbureted cars ran a 185 thermostat, but you’ll notice all the new engines run around 220 and that’s because that’s where they’re the most efficient. Before computers they ran cooler because they didn’t have computers to control detonation. A warmer, computer controlled engine, is more efficient. 

 

 

Not including when you had an issue and it boiled. 

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So there was definitely air trapped in the system. Bled the temp sensor and it bubbled quite a bit. It appears I'm still losing coolant out of the overflow though during high RPM hill climbs. Started a ride with coolant filled to 10mm over the fins as per the manual with an extended overflow hose that dumped out by the linkage (instead of all over the engine so I can see if it's leaking elsewhere). It never boiled over but at the end of the ride the coolant level was under the fins and its definitely coming out of the overflow. 

I emailed the guys at RK Tek and they think I may have a pinched compression O-ring on the cylinder.  

Edited by StreetDoctor

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23 hours ago, 69fastback said:

It should warm up quickly. The whole purpose of a thermostat is to help the engine warm up quicker, rather than keep it cool. The thermostat sets the floor, not the ceiling. Any fuel injected engine needs to be at operating temperature to fun efficiently. Carbureted cars ran a 185 thermostat, but you’ll notice all the new engines run around 220 and that’s because that’s where they’re the most efficient. Before computers they ran cooler because they didn’t have computers to control detonation. A warmer, computer controlled engine, is more efficient. 

 

 

Not including when you had an issue and it boiled. 

Any idea what temp range these things are supposed to run at then? Slavens seems to think 180-190.

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Background- bike has always ran a little hot, like most of them apparently. Installed a fan and that seemed to help a little but the fan was just always on then compared to my buddy's carb'ed TE300. I have the fan set to kick on at 190f. I just installed an RK Tek head and engine ice expecting it to run a lot cooler. I also turned the PV out 1/4 turn. All was well for about 15 miles and it started to overheat badly. Ended up pressure testing the system and found a real slight leak in two of the hoses at the clamps. Enough to lose enough coolant to make it overheat. Tightened everything up, pumped it up to nearly 2.0 bar and everything held. Went for a ride today and within 3 miles it was overheating again. Came home, checked everything again and all is tight. topped off the coolant with engine ice and rode around the neighborhood at 20mph and it would run all the way up to 190 when the fan would kick on. Doesn't seem right. It's 93F outside today but I still don't think it should run that hot when the bike is moving and it isn't under much load. 
I'm about to take it back to the dealer. The only thing I can think of is the thermostat isn't functioning and coolant isn't circulating. Anyone have any ideas? I've debated a thermostat bypass kit but I'm supposed to leave wednesday for a trip with some friends from out of state and the bike is currently not rideable. 

Have you checked your pump impeller? Maybe that’s your problem. Boysen makes a high flow impeller.

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12 minutes ago, TC686B said:


Have you checked your pump impeller? Maybe that’s your problem. Boysen makes a high flow impeller.

I’m at work until Wednesday morning now.  Now that I can tell it’s spitting coolant out of the overflow at high rpm I’m gonna pull the head and see if one of the o-rings are pinched. The guys over at RK Tek are pretty convincing with thinking it’s the inner o ring. If that doesn’t fix it I’ll check the impeller. I also ordered a Samco thermostat bypass kit. Hoping to have it sorted for a 70 mile ride Friday. 

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I cant get my tc250 to run hot enough.  

cylinder head water temps stay about 125 F with the radiators blocked off 50% or more.    

probably will look into a thermostat in the coming months.  

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12 hours ago, bentvalves said:

I cant get my tc250 to run hot enough.  

cylinder head water temps stay about 125 F with the radiators blocked off 50% or more.    

probably will look into a thermostat in the coming months.  

HAH I just took mine off. I have a strong hunch the issue was the Tusk radiator cap. I just pulled the head and the o-rings are perfect. Hoping to get a ride in this evening to verify. 

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I pulled the head this morning and the gaskets were fine. One thing I noticed when draining the coolant after swapping back to the stock radiator cap- it held a vacuum. The Tusk would still lose fluid even with the cap on. I'm going to try and get a ride in this afternoon to test it out but I think the issue was the cap. Also to note- 17-19 Thermostat bypass kits by Samco will NOT work on 2020s. The in-frame pipe is much larger diameter on the new bikes. 2020 Samco kits should be out next week. I pulled the thermostat and I'm also going to see if that makes a difference this afternoon. 

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5 hours ago, MacDaddy500excf said:

It’s the rad cap or head gasket I bet

Well.... bike isn’t overheating anymore. I beat on it pretty hard today with some real steep 1st gear slipping the clutch type singletrack climbs. It’s still leaking somewhere though... I can’t tell if it’s exhaust, coolant overflow, or the cylinder base gasket. I’m really tired of tearing this thing apart. I may drop it off at the dealer tomorrow. It didn’t look anything like this on the last ride. Hoses are all dry. It’s on both sides of the motor and only the underside of the exhaust. I don’t think it’s the base gasket it idles/runs fine. 

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2BA5FF1C-03B5-40C7-B28F-29C27559BD42.jpeg

Edited by StreetDoctor

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wait, 190*.  thats not overheating.  thats perfect for a woods bike in the year 2020.

ymmv. certain restrictions apply.  

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