Is it time for a rebuild

[solly69]

So how do i know if its time for a rebuild

My engine seems like it has lost ALOT of compression and i really ave to prime it to get it to start... i mean like if I'm blowing on the back pressure pipe i have to keep blowing once the fuel has reached the carb
Also my car dont want to start once it is hot :S

Is it time for a rebuild or is there something wrong with it?
ohh btw i have only run about 3L through it
1@5%
1@10%
1@16%

 

[brad55102]

i can't say for sure,,, because i dont have very much info here but it sounds to me like it's time for a good tune.

3L is not very much fuel, you should have 3Gallons

 

[solly69]

it seems to be tuned great

but then hey.... I'm not all that great at tunning and dont have a local hobby store to go to so I'm kinda on my own atm

i am about to be moving and were i am moving to there is a local hobby store so i think I'm just gonna take it into there and c if they will have a look at it for me

 

[basketcase45]

Take out the glow plug.
Rotate the engine through a couple of revolutions.
Does it spin freely- even at the top of the stroke?
If yes, the "pinch" has gone, and will need to be resized.
A good way to avoid this is to make certain the piston is at the bottom of the stroke after you have run it. If you would happen to leave the piston at the top of the stroke while it cools, the different metals(chrome, brass, steel, aluminum) cools at different rates, squeezing the piston as it cools, loosing your pinch.

 

[solly69]

to fix that do i just need to buy a new piston and sleeve??

ohh and it basically spins freely with the glow plug in :S

 

[jnjritz]

Yes, By the sounds of it you need to rebuild. If it spins freely or with your finger tip Counter clockwise, with the plug in. Then you need a new piston and sleeve. if the motor is that new then i would just rebuild. It would be a good learning thing for you to.
Hope this helps.

 

[solly69]

thanks heaps..
when i get the funds i will rebuild the engine. Just brought a new rig so kinda broke atm but yea

ill let ya know how i go with it
Thankyou again

 

[jnjritz]

Your very welcome just glad we could help. Thats what we're here for. If if you ever need anything else you know where to come

 

[darnoced]

Hmmm...3l and time for a re-build? something doesn't sound right there.
Maybe after like 5 gallons if you have really abused it.

 

[jnjritz]

Hmmm...3l and time for a re-build? something doesn't sound right there.
Maybe after like 5 gallons if you have really abused it.

This is very very true.

The only reason i suggested it is because it has all of the symtoms of no pinch. and i had one do that to me before. I only ran 8 tanks out of it and i broke it in right. All the pinch was gone. I rebuilt it and it solved it. and this was after i tryed everything.

But also everyone makes mistakes. i was just going by what i went thru.
What else do you think could cause it?

 

[basketcase45]

to fix that do i just need to buy a new piston and sleeve??

ohh and it basically spins freely with the glow plug in :S

If it spins freely, even with the glow plug IN, it could be a more serious problem , like, for example:

- the head has come loose,
- the glow plug is loose, or bad (leaking) (( is it a turbo?)) get a new one
- there could be a crack in the block
- crack in the piston (unlikely, but possible, if extremely overheated)
-scored piston/ sleeve (deep scratches in the sleeve, from a foreign object, like dirt)
- just a few things it might be;

:\

 

[solly69]

so basically ur saying pull it apart and have a decent look at everything and then seal it as i put it back together???

It also wont start after its warm i have to let it cool before it will start again :S

 

[basketcase45]

so basically ur saying pull it apart and have a decent look at everything and then seal it as i put it back together???

It also wont start after its warm i have to let it cool before it will start again :S

That is a "classic" sign of needing a "pinch". Nitro engines, like full size car engines, are designed to operate within a certain temperature range. When it is within that range, all the parts are expanded due to the heat, and work together as they should. When YOUR engine is hot, the sleeve and piston are not making a good seal and making it hard to keep it running or keep a tune on it. I have used OSROCKET ( http://www.osrocketracing.com ) for several nitro motor resizings and have been well pleased with the result. You will have to do a short break in again when you get it back, but it will run as good as new again.