Savage S-25 engine hard to start when warm

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ArcticSnow

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13
I know I've seen this thread somewhere, but I can't find it. So sorry about that. But well,title says it all. It coughs and fires but it's kind of a pain to get it to actually start. I know I'm using a drill to start it, and drills "don't spin fast enough", but if it can start it cold easier then it can warm, I feel it's a tuning issue.
 
Odds are it's a wear issue. As the piston wears, the fitment of it and the sleeve aren't tight enough when at running temp, which causes blow by, flame outs and hard hot starting.

If your comfortable with taking engines apart, you can check the pinch by taking the sleeve/piston/rod out and orienting the piston in the sleeve properly then with gentle pressure, push it up in the sleeve and see how far it goes. If it reaches the top or beyond with minimal force, it's worn out.

I have a few photo's of mine before I had a re-pinch done (which is also a cheap option to get a few more gallons of life):
Before re-pinch:
2008-0315-XTM247-Mach427-SH28-SleevePiston01.jpg

2008-0315-XTM247-Mach427-SH28-SleevePiston02.jpg


After re-pinch by RayARacing:
2008-0327-RayARacingAllThree.jpg
 
I have a lrp .32 that is impossible to start when its hot. You can actually hear fuel boiling in the carb despite the temps and tune being good. Fuel would be forced back down the fuel line toward the tank. I was told it was caused by the uninsulated carbs that lrp used back then. (I think it is a spec 2). I also had an old savage 25 that would do the same thing although not as bad as the LRP. It would drive me nuts so I would take some pressurized nitro cleaner and spray it on the carb neck and it would start up right away. I don’t advise you do this, super cold hitting a hot nitro engine could lead to trouble but I didn’t care cause I hated that engine!
 
I have a lrp .32 that is impossible to start when its hot. You can actually hear fuel boiling in the carb despite the temps and tune being good. Fuel would be forced back down the fuel line toward the tank. I was told it was caused by the uninsulated carbs that lrp used back then. (I think it is a spec 2). I also had an old savage 25 that would do the same thing although not as bad as the LRP. It would drive me nuts so I would take some pressurized nitro cleaner and spray it on the carb neck and it would start up right away. I don’t advise you do this, super cold hitting a hot nitro engine could lead to trouble but I didn’t care cause I hated that engine!
I've had that too. Even at normal temps (220F-260F), if it stalls or runs out of gas, you either have to let it cool off a bit, or hold the throttle wide open and rip the cord quick a few times. Pretty much all engines do that that have an alloy carb without an insulator.
 
Re-pinching should not be an issue as the piston (when cold) is supposed to be a slightly loose fit. An ABC engine is designed so that the piston ( A in ABC) expands at a faster rate than the sleeve (B in ABC) which in turn seals the bore at TDC due to the tapered bore of the sleeve.
This is why we need to “run-in” an engine, the piston, when new, is too tight and would seize with a normal tune condition.

Your problem may be due to the fuel vaporizing in the carb/lines when the engine is hot. I run my fuel lines away from the engine as much as is practical.

Cheers.
XL
 

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