[Mjleedle]

Son and I finally had time to get the bikes out for a prolonged period. After about an hour of sustained casual trail riding. Up and down some rollers and some 25-30 degree climbs (50 or so feet long), I pulled out the IR thermometer I use on to heck the vw motor. Cylinder and head were 320 degrees. Doesn’t sound too far off from the vw but just wanted to double check if anyone knows the temperature range? I couldn’t find anything in the service book.

[JimDirt]

I would guess the water temp itself would be in the 200 - 250+ range going slow like that , possibly higher , so I would imagine the actual head temp would be in that same range ......... the engines need airflow thru the radiators to cool , the slower you go , the higher the temps will be because the air is not "flowing" thru the radiator , period ... the only way to avert that is to add a cooling fan setup (needs a battery to run), that is thermostatically controlled , I am not sure if Trail Tech offers a fan kit for that bike , but they do make them for the 250x and 450x , and for the new gen 250/450 R and RX , if you want to keep the temps down while riding slow stuff that is really the only option aside from higher temp radiator cap (which will not lower the temp , but raise the boiling point before blowing past the cap and spilling coolant) , also Engine Ice coolant , or Evans Waterless coolant can actually lower the operating temps by 50 degrees .... , so to answer your original question , I do not know the actual temp range of the head , but I do know for a fact that riding slower tougher places will raise the temps fairly quickly and fairly high to the point of boiling over , I know as the ambient temps increase the closer we get to summer , the faster/easier they are going to boil over/run hot , I run a fan on my 450X for just that reason .............

[Mjleedle]

Thank you Joe. The 100f is an air cooled motor, so mainly just wanting to make sure it’s not running too lean. At least I assume like the VW motors they run overly hot when lean but cooler when run a bit rich. When I opened the carb to fix the float I found a Chinese rebuild kit, with new float that was bottoming out before it shut the valve and unmarked jets. Plug looks ok, possibly a slight lean so that’s the main reason I was asking.

[JimDirt]

My bad on the Air cooling I did not look up the specs on the 100F , it is derived off the old XR format then .... now I am following .... ..... But same holds true , air flow is still the cooling factor , so if no radiator , then no fan , , but no air flow with air cooled , still no cooling effect , so basically you are kind of stuck with trying to keep it cool if you continue to ride in the slower stuff , if the engine is not hanging the idle after it gets hot , I would suspect the pilot is not too lean (pilot would control the fuel when going slow or idling , since you are creeping along , then the pilot would be the issue if it was lean) , you could try adjusting the fuel screw (out is richer) and see if that helps the temps some , but basically , when you go slow , it is going to get hot , how hot is up to the ambient temps and the speed you are going , if it is at a crawl , maybe take some breaks to allow the engine to keep cooler , or break from the tight stuff and hit some more open areas to allow it to cool down and not constantly run in the hot range , that will help the engine live longer , as constant heat will eventually cause issues with piston scoring , ring failure (loss of compression) and even seizure if abused long enough ....

So try the fuel screw and see if you gain some cooling , it won't solve your issue , but other than going to a 2 stroke (which can sit and idle for days without overheating compared to any 4 stroke) you don't really have a lot of options ......at least nothing that will really make a huge difference ...

Oh ... even though my name was derived from Joe Dirt the movie , I am JimDirt not Joe ..... .... easy mistake ...

[Mjleedle]

Sorry ‘bout that. I thought I typed Jim...

2t is the potential hope. He can take my 200 xc-w and I’ll get a new TPI 2T. But he will have to grow from his current 5’1” 90lb frame.

[JimDirt]

No problem .... just kidding anyway ..... Yea maybe a 150 would be good , they have plenty enough power to hold when he gets older as well ...... too bad Honda did not keep the 2T's going , they are missing out on a huge market ...... at least they are starting to get it right with the 250/450RX , and still having the L , and the Rally and the X and the R's , they are at least somewhat listening

They did a survey (Honda) a few years ago , my request was a 6 speed wide ratio CR250X 2 stroke , basically the same as the Yamaha YZ-X model ..... They did not listen , or at least are dragging their feet on it .... I know lots of people that would buy a 2 stroke Honda if they put them back into production .........

A guy I ride with every weekend has 1, 95 CR250 , 2, 02 CR250's , and 1, 07 CR250 , he loves them all ... (he also has a 03 KTM 520 XC-W , and a 07 Suzuki RM250 and a 18 Suzuki RMZ450) I wish I had his money

Anyway , yea you are kind of limited with the bike you have , unfortunately

[Aussiecrf230]

From memory anything in the 300-400 degrees F as a maximum normally taken at cylinder head on spark plug boss.

Seen them go another 50-80 degrees hotter before detonation. This was old 2 stroke engines with castor oil.

The big thing with any 4 stroke is that the oil temperature doesn't exceed what the oil can handle.
Synthetics are better, but not hugely better.
Running it richer at wide open throttle full load is always going to provide internal cooling.
There was one engine that it was best to leave a step at the valve insert so the incoming charge would pool there and keep the seat that bit cooler so it didn't crack and fall out.

[Mjleedle]

I only paid $500 for his as a beginners bike. He’s 14 almost 15 but very small stature, though he has grown 4.5” since I bought it last November. Figured he would be too scared to ride it, though I made him a promise if he got all As in his HS AP classes (he was in 8th) that I would get it for him. To my surprise he has taken to it. About 10 hours into riding it so far and finally shifted to 2nd...

[JimDirt]

Hey , James Stewart and Ricky Carmichael are both only 5'6' , so there is hope for him , as long as you are moving , your feet don't need to touch the ground ........... Funny , when I was in Junior High (very early 70's) I was 5'11.5" , now at 60 , I am 5'9" due to multiple broken backs and a broken neck , all shrinking me down , I already had short legs , all my height was body ..... but even at 5'9" I struggle to touch the ground with one tiptoe on these newer bikes ..... one of my riding buddies is 6'5" and 320 lbs , he looks like he is riding a 60 when he rides his 450 ...... modern bikes were not designed to accommodate short stature people , or specifically people with shorter legs , the seat height on most full size bikes is over 36" , that does not help someone like me with 32" legs , on the opposite side of the coin , they were not designed for tall people either ...... So unless you fall into the "average" category , you will struggle with bike comfort/fitment ......

My buddy that I mentioned earlier did not start growing real tall till he was 21 , but when he got his growth spurt it was all at once , then he went from 5'9" to 6'5" in 1 year , so your kid may be a giant suddenly and soon be complaining they only make bikes for "normal" people and not tall people ...... or he could be short and have his subframes cut down , like James Stewart , Ricky Carmichael , Ryan Villopoto ,Ken Roczen , and several other pros who never got "tall" have had done , and all went on to win Championships .....

Look how big my buddy looks on his 450


This is Rick Smits , the basketball player , look how he looks on a 450 , he is 7'4"


So being taller isn't all it is cracked up to be either ....