Honda Spree and Elite 50 Forums

Ok now have a Honda sa 50 p overheats its running a 50 mm piston stock carb 78 jet pre mixed in tank and stock oil wide open racing cdi no rev limit I'm no mechanic I'm just learning and have gotten pretty good at ripping this scoot apart and putting it back together it's a 2001 all restrictors have been removed but can't figure this one out about to rip it apart again and find out why it won't start and while I'm there I'm thinking about cleaning it all shining it up and opening up the front plate I'm thinking when the first build blew it left little prices of metal in the bottom that float back up and compromised my last 2 rebuilds the last 2 cylinders were scratched and over heated any ideas guys it's driving me bonkers and can't afford more rebuilds lol

pun intended......your main problem I imagine is your main jet that is waaayyyyy to0 small depending on what kind of intake and exhaust you have. You should at least be running a 100......rich is a lot better than LEAN. Running your engine lean will cause it to overheat, the gas no only combusts to move the piston but it also cools the engine in a sense...the oil just keeps it lubed up reducing friction. You may want to consider removing the oil pump entirely, plug the hole and run 32:1 premix in the tank hope this helps

Ok plug the stock oil sounds like good idea as I'm never sure with that oil pump anyway any ideas how to install a temp gauge to gt an accurate on the temp and what kind I might use Im pretty sure the temp is a consistent factor in my cylinder demise ,, and what about the pieces of metal as my last build the rings were well looked like filed down to flush with the piston ... And cylinder was scored

you can try to flush it out with the cylinder and piston off, slosh some gas around in there or whatever solvent works for you BUT it wont be completely clean unless you split the cases. there are several temp gauges you can get. If you are going to spend the money go with the trailtech vapor it does almost everything. speedo, temp, rpm, odometer not sure exactly all the functions. surf ebay for temp gauges and you will get an idea of the prices and brands. I use a digital foodservice thermometer with a long probe on the end hahahhaha but i have to stop to check temps. you will need a 14mm round adapter that screws under the sparkplug not sure if the gauges come with one or not. VT cycles in hawaii has pump plugs for 10 bucks plus shipping and most likely has a main jet kit to tune with. also make sure the clip on the main neelde is in the middle or on the bottom, if its on the top then it is even more lean. The idle/pilot jet on the stock sa50 carb cannot be changed so with your engine leaned out at the main it makes it even more prone to overheat on idle or right off idle. I am sure there are others here that could give you way better advice and maybe they will chime in later in the day. I am by far no expert but these are some of the basic things to be aware of. Did you drill out the washer in the exhaust header or modfiy the airbox?

Mystic is 100% correct. Your main jet is the problem. Run a 100 or 105 and that will solve the overheating problem. Also break the 50mm kit in slowly and you will get long life. If you try to WOT a new 50mm around it will soft seize. If you soft seize over 3 times then the kit is usually no good after that.

Taz

Greetings:

The 78 is much too small, as previous responders have suggested. However they are not "100%" correct.

The other problem is not so easily addressed: The Pilot jet is too small. When you let off the throttle and that bigger Main no longer contributes its share to the intake stream, overheat occurs on coast-down. Seems odd that the greatest damage is produced when the engine is producing no power, but true just the same. The PA Pilot circuit is cast-in and can't easily be modified except by removing the standpipe - itself not easily accomplished - and drilling the carb very precisely to a larger size. How much larger? No one really knows.

Better to locate and install a nice Amal/Arreche-for-Honda 21 mm carb or swap the intake for an OKO manifold and OKO carb to permit accurate low AND high-speed jetting. Stock carbs on an 82cc setup Greetings:

The 78 is much too small, as previous responders have correctly suggested. However they are not "100%" correct.

The other problem is not so easily addressed: The Pilot jet is too small. When you let off the throttle and that bigger Main no longer contributes its share to the intake stream, overheat occurs on coast-down. Seems odd that the greatest damage is produced when the engine is producing no power, but true just the same. The PA Pilot circuit is cast-in and can't easily be modified except by removing the standpipe - itself not easily accomplished - and drilling the carb very precisely to a larger size. How much larger? No one really knows.

Better to locate and install a nice Amal/Arreche-for-Honda 21 mm carb or swap the intake for an OKO manifold and OKO carb to permit accurate low AND high-speed jetting. It is very hard to achieve reliable performance from an 82cc Tai cylinder anyway, but running the stock carb it's just about impossible. Your Mileage May Vary.

All these carb experts= what is your gear ratio

maddog wrote:All these carb experts= what is your gear ratio

Absolutely irrelevant to this issue.