YM1700 overheating

[Bigpine]

New here.
YM1700
I did a upper rebuild last fall, new loaded head, pistons, rings, injectors and injector pump, radiator with new over flow tank. About 5 hours on it since rebuild. Some light colored smoke at first but mostly goes away. Started overheating recently after about 30 minutes of use. No bubbles in water, no water in oil or oil in water. It will force water hard out of the overflow tank on startup, the old tank cap does not have this bib it’s sealed. I have the upgraded water pump kit installed but it’s old and seemed to feel ok at the rebuild. The old radiator was in bad shape, so I replaced it, yet with a cheaper knockoff from eBay, though it looks well built I wonder if it has the same tolerances, has anyone had issues with these? I have not retorqued the head yet so will do so, going to try a new radiator cap and the old over flow cap. Tightened the fan belt but still hot. Suspect; water pump, radiator, radiator cap and tank cap. Thoughts, or experience with those radiators or anything related appreciated. Also, I have a separate issue with the governor on high rev after pulling back on the throttle it will stay at high rev and not come back to idle right away, thinking it needs adjusting?
Thank you

 

[bmaverick]

New here.
YM1700
I did a upper rebuild last fall, new loaded head, pistons, rings, injectors and injector pump, radiator with new over flow tank. About 5 hours on it since rebuild. Some light colored smoke at first but mostly goes away. Started overheating recently after about 30 minutes of use. No bubbles in water, no water in oil or oil in water. It will force water hard out of the overflow tank on startup, the old tank cap does not have this bib it’s sealed. I have the upgraded water pump kit installed but it’s old and seemed to feel ok at the rebuild. The old radiator was in bad shape, so I replaced it, yet with a cheaper knockoff from eBay, though it looks well built I wonder if it has the same tolerances, has anyone had issues with these? I have not retorqued the head yet so will do so, going to try a new radiator cap and the old over flow cap. Tightened the fan belt but still hot. Suspect; water pump, radiator, radiator cap and tank cap. Thoughts, or experience with those radiators or anything related appreciated. Also, I have a separate issue with the governor on high rev after pulling back on the throttle it will stay at high rev and not come back to idle right away, thinking it needs adjusting?
Thank you

You need the overflow cap. The cooling system is pressurized. On these overflow reservoir tanks, the cap is typically a pain to take off as these hold on very tightly.

Light colored smoke and then clears up could be soot build up in the exhaust manifold into the exhaust pipe.

This is straight out of the YM service manual when replacing the head gasket . . .

 

[Bigpine]

Well, I solved It. I had the water pump hoses reversed on the pump. Duh!!! I did the rebuild over the winter and with lower temps it never overheated then. I just hope I didn't do any serious damage as it did get over 200 a couple of times earlier this week. I worked it good yesterday for about an hour and the temp was great and it ran fine.
I knew about not running at WOT, rarely do anyway, but didn't know about staying away from low idle, thanks.

 

[bmaverick]

Well, I solved It. I had the water pump hoses reversed on the pump. Duh!!! I did the rebuild over the winter and with lower temps it never overheated then. I just hope I didn't do any serious damage as it did get over 200 a couple of times earlier this week. I worked it good yesterday for about an hour and the temp was great and it ran fine.
I knew about not running at WOT, rarely do anyway, but didn't know about staying away from low idle, thanks.

The engine can survive 200F. It's below the 212F boiling point.