Cylinder Head running too hot 350-360

[suther1707]

1997 Elite SA50
9:1 gears/keli variator
72 cc Polini overbore
28 mm OKO 55/140 (w dual reed intake manifold)
air screw 1 1/2
jet needle middle position
v8 exhaust
32:1 Honda GN2
Stock clutch/springs
trailtech vapor speedo/rpm/temp gage.

This is my first post to the site. I have used the site many times in the past couple of years as I upgraded the Elite SA50. I have unfortunately already been through a 50 mm overbore. It ran about 1200 miles but the heat was too much. At that time I was running stock carb w/100 jet and exhaust. I started all over and got the polini. I don't want to overheat this one so I have been watching the temperatures. It gets in the 350-360 range after riding non-stop for about 3 miles at 50 % throttle. It doesn't decrease when I go WOT but doesn't seem to get much worse. I always back off of the throttle and let it cool down. I haven't taken it any further than this until I can get a handle on the temperature. I have upjetted the pilot to 55 and the main to 140. I am considering moving the jet needle position down 1 or ordering a bigger pilot and main. Any advice would be greatly appreciated. I would like to run no higher than 300 degrees.
suther1707

[Bear45-70]

Raise the needle.

[mopro logan]

I have seen a couple of post that said that lipid to thin and results in higher temps. Not sure if that is true or not but might be a possibility.

[suther1707]

Thanks for the replies thus far. I need to add that I am running a ngk BR8hs plug and I meant to say that I am lowering the clip to raise the needle one position. Wandered if anyone else is running this setup and what jets they are using. I need some kind of ball park.
suther1707

[mopro logan]

That is the same plug I am using . I think trafficjamz has a build that is close to that I would pm him and ask what he might know.

[dun rite]

read a while back on the forum that using maxima castor 927 oil lowered someones engine temps by 30 degrees. what type oil you using?

[Petrock's 1984 Spree]

read a while back on the forum that using maxima castor 927 oil lowered someones engine temps by 30 degrees. what type oil you using?

That'd by my CHT temps

That 927 stuff is great. I used the GN2 a while too and its too thin for a 72cc bore. Put thicker oil in.

Youre temps will drop and you'll be able to jet a little leaner for a bit more performance

[suther1707]

honda GN2 @ 32:1

[Petrock's 1984 Spree]

I would like to run no higher than 300 degrees.
suther1707

Unfortunately that Polini bore lives above 300F. If you want your temps to be no higher than 300F at WOT you wont do it with an air cooled elite with a 72cc engine on it.

You could go water cooled but thats $$.

350-360 isn't bad at 1/2 throttle. You just want to stay under 400F at all parts of the throttle and you'll be alright. I'd upgrade to using maxima castor 927 regardless

[suther1707]

Ordered the Castor and will give it a try. I'm not seizing but want to insure that I do not do so. I want to keep the bore in the safe zone. From what I read that's below 350.

[Trafficjamz]

350-360 isn't bad at 1/2 throttle. You just want to stay under 400F at all parts of the throttle and you'll be alright

I agree those temps are not too bad.

Your 9:1 gears may be a bit to short for that polini bore.

It likes to rev....and 9:1 gear might rev it too high.

[suther1707]

Running at about 9000 rpm wot. By the way it runs really great as far as acceleration through wot. I like the acceleration and really won't use top end speed very often. I like riding around 40-45 on open highway but most of the time I'm in the 25- 35 mph range for in town. Faster than that and the scooter suspension seem inadequate to handle well. I may look into improvements to the suspension/tires to improve handling after I get past the heat issues. Current top speed is around 55 mph.

[Trafficjamz]

I run my polini with a 55 pilot and a 142main on a 28mm carb.

I have a pg long pipe.....so the jetting will be different.

[guen84]

i have a little bit bigger set up to compare, but i was having temp problems at long 1/4-1/2 runs moved needle up (or clip down). some times after you do that you may need to lower your pilot. you wont have much for performance at 300 deg. them polini bore run better on the hotter side..

[suther1707]

Again thanks for all the replies. When the Caster 927 comes in I'll post the temp. results in comparison to the Honda GN2 for heat reduction. It looks like I need to set my target high temps in a higher range. I'm seeing up to 400. I've read that above 350 is the danger zone. Any comments on problems with soft seize temps on the 72 cc polini would be helpful to set up top temps. Again I don't mind running hotter as long as the bore isn't being damaged or life reduced. I would like to be able to make some long runs 40-50 miles anyway. I am considering the comments on gears too but if I can get the temp under control, then I will stay with the current set-up. Technically the gears are 9.8 to 1 (15*42).