Topic: engine temp

[svenD]

hi all
anyone know why the motor seems to run best just before it reaches peak temp.?
- most noticable on hot days,
- I hav seen it on several bikes,thouge it seems less pronounced on my faithfull 550K

[Gordon]

Probably because on hot days it's actually getting hotter than its ideal running temperature. 

[svenD]

- what would you think constitutes a "hot" day ?
-here in denmark 25degrees C and above meets that criteiaria,   
 -shurly honda expected there bikes to meet higher tempretures than that without any sweat.

[Gordon]

I wouldn't consider 25C hot.  More like 30 or above. 

Air-cooled engines run at various temperatures based on several factors, one of which is the ambient temperature.  There is a temperature range where the sohc4 engines will run best, and that is the temperature that things like jetting, valve tappet gaps, and all other clearances between moving parts in the engine are designed for.  When multiple parts have worn past their factory specs you're going to experience changes in how the bike runs from the way it ran when brand new. 

In addition, carburetor and jet problems, as well as valve issues can cause the engine to run hotter than it normally would under a given set of conditions. 

[svenD]

-would a slightly lean mix be better than slightly rich?
-would low and mid range torque be more affected by the conditions (wear % such) you have ststed,

[Gordon]

Slightly rich is generally better than slightly lean because it lowers the temperature a little. 

Don't really know on the second question.  I guess it would depend on the bike in question and the amount and type of wear it's experienced. 

[svenD]

thanks gordon

[Gordon]

thanks gordon

You're welcome.  I'm definitely not an expert on this, though.  I'm sure someone like Hondaman could give you a point-by-point breakdown on all the individual systems and how wear and various temperatures affect each of them and the overall running of the engine. 

[Gaither]

FWIW

If you really want 'em to cool better, paint all finned parts FLAT BLACK.

Ain't as pleasing to the eye but black transfers heat [cools] MANY TIMES better than silver or any light color. [Mine's still silver].

Years back Hotrod Mag. tested this fact extensively on auto radiators. 'Can't recall the numbers but black won hands down. There is a DRAMATIC difference.

Actually, any dark color would cool far better than silver or light colors.