Motors Trex 700

[Island Breeze]

My Trex 700 wont crank over..So I changed the plug and still no luck. im no mechanic so your help is needed.

YS .91 SR 3DS



I took the head off and low and behold the piston has some nicks and chips. yes the motor had little compression before. would a motor not crank over if it is loosing compression?

 

[danhampson]

wow your sure getting into the nitro thing.

 

[Tony]

Those marks are more than likely caused by the last owner taking the crank nut off. You have to lock the piston in place and some just use a screw driver. By the way, this is a BAD idea lol. Stuffing something like a towel or a shirt in there is better, but the best option is to get an actual crank locking tool. This shouldn't cause it to not crank over though.

Check your batteries in your starter. Remember, this is a 91 size engine and it has LOT of compression. Look at what Gaba went through. He tried to start his 91 on his Align starter, and it just didn't have enough strength. So he had to get a stronger starter.

Check your ring. If it's a nice shiny, almost chrome look, then you need to rering the engine and hone the sleeve. If there are still some black spots on it, then it should still be good.

 

[pvolcko]

Loss of compression can keep it from starting up, but you should at least hear it popping a few times like it wants to go, it just won't keep going and if it does run it will be sputtering and weak. That said, a little piston head damage shouldn't affect compression too much, that is really provided by the piston ring to cylinder wall interface. If there are scratches there or other signifciant damage (warping of the rings, etc.) then that will cause loss of compression. Have you taken the piston out to inspect the rings and cylinder wall? Any idea what got in there to cause the piston head damage?

...

Just saw tony's post, is it not turning at all (seized)? Or is it just not firing up when the starter does turn it?

 

[Island Breeze]

wow your sure getting into the nitro thing.

Ya! a matter of fact both the Protos and Gob will soon be hitting the for sale section soon. just a change of pace

- - - Updated - - -

The sleeve has no scratches at all and I do have a pretty heavyduty starter so those two are ruled out for now. Oh it cranks over it just wont fireup.I will probably check into the align 2-1 regulator/ignitor tonight. thanks fellas

 

[Tony]

If this happens again, pull the plug and cap off the fuel line. Spin the engine over quite a few times, stick the plug back in it, unplug the fuel line and try to start it again. It very well could have been hydrolocked.

 

[Island Breeze]

If this happens again, pull the plug and cap off the fuel line. Spin the engine over quite a few times, stick the plug back in it, unplug the fuel line and try to start it again. It very well could have been hydrolocked.

No hydrolock I think. I can hear the motor turning, its just no firing up. Grrr! between this and the 600N Gov issues, I just need to fly. I think ill just bring the GOBBY to the field to fly also.

 

[Tony]

Okay, make sure your carb is open enough, make sure you have a good glow plug and that the igniter is lighting it up. Also make sure there are no leaks in the carb base and back plate.

 

[Island Breeze]

Going to fly tomorrow..got football game today. Yeah baby!

 

[coolgabsi]

I actually just got a Better battery for the starter. Still the align starter here.

If it doesn't crank over, check for play in the crankshaft pin on which the piston rod rides.. Too much give, or wrongly installed backplate, or bent piston rod could all cause the engine to not turn over.

If none of that, put a little bit of bearing oil through it abd run it with your hand .. Make sure those chipped piston peices aren't in the engine

What does the piston ring look like?

 

[Island Breeze]

The bearing shattered on the last owner. it was replaced and cleaned. the sleeve looks clean, I am not to sure on the ring, shaft etc. I will have to take it apart. the love of the hobby.