Originally Posted by
fizzy
I am a bit concerned I've damaged my b5, took it out yesterday to see how everything was after having a short break and about 15min in the car took off at full noise, I was in such a rush that I didn't haven't an elastic band on my carb as a safety and turned out it was a faulty connection on my switch that cause the rx to loose power thus sending the car off at full noise . It ended up hitting a fence and landing on its lid but was screaming for a good 30seconds before I could get to it . I shut it down and man was it HOT. The engine and pipe were smoking and the fuel was almost boiling . I put the temp gun on it when I got it back to my tools about 2min later and it was giving me about 170 so it must have cooled somewhat on the walk back . I pulled the plug out and the element was literally scorched almost to white dust it looked like, when I got home I pulled the engine down and everything's seems ok bar the top of the piston and the head button are a light greyish colour and almost look like there is some really tiny what looks to be little pits or kind of rough but really lightly if this makes sense. Have I lucked out and saved the engine or not. I can't upload pics and am really disappointed cause I love this mill and really wanted to get a chance to enjoy it. I have cleaned everything and put it all back together , engine still has nice comp and sleeve and port seem ok. Should I just fire it and continue to run it and see how it goes?
As Jerm mentioned just put it back together and run it. Engines really do not cool down that quickly so if you tempted it after 2 minutes and it was showing 170F then it was probaly only in the low 200's which is safe. The white coloration of the glow plug is actually good, that means that your engine has been running properly tuned (there would be black carbon build up if it was running rich, or a dull grey deformed glow plug element if it was running to lean). The slight pitting on the head button and top of piston is indeed an indication of the fact that at one time the engine was run lean (the pits come from pre-detonation, basically the early ignition of the mixture charge before the piston gets to TDC).
The runaway depending on how long it was going unloaded could have stretched the rod. My suggestion though is put it back together, richen the needles a few hours to be safe and then re-tune from there. If you engine seems unusually tempermental and difficult to tune and is pre-detonating then you may have a rod issue, if everthing runs fine then you are ok. My guess is that you will be ok! Let us know how things go...