Hot start problems

[Kaiser]

I'm pretty new to nitro rigs and bought a second hand savage x 4.6. When I got the truck the previous owner couldn't get it running so I went through it and tightened/replaced all the engine screws and gave it the once over. Replaced a cracked one way bearing, and a broken starter spring and pin. I have gotten the rig to start and have tuned it in a bit so it starts nice cold. Runs about 220deg F. If I crash and can't get to the truck before it dies it has a real hard time starting. I don't know where I've gone wrong. Of the few times I've gotten to run it It had been running good, but was burning through the clutch. So I replaced the clutch shoes today. Got it started and it ran great. Wheelies and good power to the ground. Bumped into a pallet and hot stuck, before I could get to the truck it died and would not start. Didn't want to burn up new OWB so I quit. Pointers?

 

[olds97_lss]

You may be running a bit lean causing the fuel to boil in the carb when it's hot. Usually holding the throttle about half throttle while trying to start will dump enough fuel in to cool it and get it going, just let off the throttle as soon as it fires.

That said, hard starting when hot suggests it's lost a lot of it's pinch and your getting too much blow by once everything is warmed up to operating temps. Maybe time for a new engine or at least a re-pinch on the old sleeve.

This thread of mine kind of shows you what pinch is, in case you don't know:
https://www.rcnitrotalk.com/forum/showthread.php?t=56420&highlight=pinch

 

[Kaiser]

Thanks. Sounds like more money have tried the half throttle start with mixed results. Will keep at it.

 

[olds97_lss]

If your capable, take the engine out and take it apart and gently push the piston up with your hands through the sleeve to see how far it goes. If it easily reaches the top or sticks out the top, it's pretty worn and your going to soon have problems just running it.

You can see the photo's of mine in that thread I posted of the "before". If yours does what the Dynamite and SH did, then I'd send it in for a pinch (all info in that thread to send it in) or get a new engine.

 

[BillyC74]

This won't fix the hot start problem but if you put a longer fuel line on it, it will run longer upside down. I've probably got 12 inchs on mine. It will run for plenty of time for me to get to it.

 

[Kaiser]

Great! Thanks fellas. All good info. Will be tryin it tonight. Have had the engine out enuf times now I think I can do it blind. the longer fuel line is a nice idear as well. Super.

 

[olds97_lss]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFUD3&P=7
Those add some rooftime as well. I have on on my savage, revo, ofna buggy and jato. I use 4 zipties. Two to keep the bulb snug with the input/output plug and 1 on each fuel line.

They also make it really quick/easy to prime.

 

[Kaiser]

I think that some of my problems are coming from crappy/old fuel. What is shelf life on nitro fuel? Suggestions on brand and nitro content?

---------- Post added at 10:29 PM ---------- Previous post was at 10:25 PM ----------

Also what is good temp to shoot for? Book says 250 is danger zone. I would rather run a safer/longer engine life tune than a balls to the walls super performance tune.

 

[BillyC74]

Fuel shelf live seems to depend on how it stored. Like keeping it in a place with consistent temp, keeping it out of sunlight and the such. I can't seem to keep it around long enough to test the limit on self life. If its in doubt get new. I run Byron Fuels Race Gen 2, 20% nitro 12% lube. It has worked great for me. As far as temps; 300 is the absolute MAX. My X4.6 never runs hotter than 240 when tuned properly. Hope this helps.

 

[Kaiser]

Sure does, thanks. I have been runnin traxxas as it is what I had from a previous truck. Been in my basement in the dark for 5-6 years. I was recommended Danielson fuel? Will see what's available at the local hobby shop.

 

[Kaiser]

Got some new fuel today, holy huge difference. Idles better, good throttle response, starts nice. Like a whole new rig. Thanks for all the help folks.

 

[BillyC74]

That's great! What fuel did you end up getting?

 

[Kaiser]

Blue thunder 20%. Seems to be working great.

 

[BillyC74]

Good deal, I've heard thats good fuel.