Do i need a rebuild?!...carbon...

[s00045732]

right story goes i bought a crashed 94 rx7 for a transplant was told the car had been rebuilt about 3yrs ago, the car was crashed 2years ago, (owner emmigrated) and not started in about a year and a half.........
 
wel i got her going tonight and started up with the usual blue smoke but cleared out after a few minutes when it warmed up BUT was tickingover like a tractor....bap...bap...bap....bap if that makes sense and blows a bit of blue smoke when you rev it anyways hard! it also was turning over quite slow before it fired!
 
now me knowing nothing in particular tought it was compression and tough apex seals.... rebuild... so i rang the lad i bought it of to give out to him (i no him)
 
now he said after he crashed and moved away his dad used to start it up and let it tick over for 5-10 mins and then turn it of to keep it \'fresh\', he said it couldnt be the apex seals as they only have about 15000 miles on them and it was proberly just carbon build up that is causing the bad compression??
 
is he jus fobbing me of or do you think he could be on to something?
 
any help welcome, thank you in advance,
Paul

[L18M]

bap...bap...bap.. OR brap...brap...brap?? :rollin
bridge port?

[s00045732]

nope not bridge ported and definley bap bap bap :Giggle but thats sort of sound... maybe if i closed my eyes forgot about the smoke and just imagined it was bridge ported, it does sort of sound similar! :rolleyes: couldnt think of how to write it down lol

[Ed_RX7]

does it sound like a tractor?

[stacy]

Have you compression tested it to get the exact numbers? (I think how to do this is elsewhere on here).

If it\'s been idle for that long, and used only for short bursts then, there may be merit in the gook argument?

Alternatively seals may have perished? :-(

S.

[s00045732]

yup it sounds like an ould massy fergson tractor on idle - must easier way to explain it! but sounds smooth when you hav a constant rev on
 
no i havnt done a compression test yet il have to borrow a tester but i am almost sure it is down on compression
 
is there anyway of clearing this apparant build up without stripping the engine?

[stacy]

yup it sounds like an ould massy fergson tractor on idle - must easier way to explain it! but sounds smooth when you hav a constant rev on
 

Ah...

Tell you what, rather than risk damaging it properly why don\'t you just spend a weekend stripping and inspecting?

S.

[sparky_ssr]

You running it on the old fuel? Fuel has a very short shelf life. Stick some optimax in it, let it warm up and id be half tempted to give it the limiter to try and get rid of the carbon build ups caused by long idle periods. That would be up to you tho. Sensible things like stated would be compression test or a weekend inspection.

[m1tch]

You running it on the old fuel? Fuel has a very short shelf life. Stick some optimax in it, let it warm up and id be half tempted to give it the limiter to try and get rid of the carbon build ups caused by long idle periods. That would be up to you tho. Sensible things like stated would be compression test or a weekend inspection.

If 1 of the rotors has gone, starting the engine up will just damage the housings

[Grizzly]

Have you done the Curb side Compression test?


1 - remove the top plug out of a rotor
2 - remove the EGI fuse
3 - crank engine
4 - get someone to listen for 3 even Psssh noises
5 - put plug back in
6 - remove other top plug
7 - crank and listen

You are looking for three Pssh noises per rotor, they should be evenly spaced (and timed) between the two rotors and Pssh noises should be the same volume on each rotor and very similar front to back.

If you get no Pssh noises on one rotor you can try the Coke or ATF trick but 9 or out ten time it means a rebuild.

Does it sound like a Tractor all the time? if you rev it or on idle?

My personal opinion is as long as you have oil pressure there you can\'t really do much more damage than there is already trying it, if the Apex\'s have gone you are going to have to replace the Housing and Rotor anyway?

There are so many things it could be, you need to eliminate the big ones first.

[m1tch]

Im guessing its only like a tractor on idle, then when it revs up the centrifugal force moves the apex seals onto the housings sealing the chambers - its why if you blow an apex seal you only notice it at low revs or when you come back down off the redline

[s00045732]

thanks everyone,
 
yes its only like that on idle, i put a good drop of petrol in it there and ran it for about 15mins there and smoke has cleared and sounds slightly smoother, have to do a compression test at the weekend, what is the coke or AFT trick?
 
im proberly going to strip it if i dont get a nice idle soon i dont want to risk a housing or rotor, plus it will be a good excuse for a bit of porting

[Grizzly]

Here is a write up of the ATF trick, you can use Coca cola or diesel instead of the ATF. I have used all three and fined the Diesel works best if you put about two tea spoons in each rotor bath let it stand over night then spin the Engine over with the plugs out for 10 seconds (with the EGI out) then start.

http://www.mazspeed.com/atf.htm

I personal Don\'t like using ATF because it fouls you plugs up and makes restarting a pain, i would recommend doing one rotor at a time (mainly the bad one first) so your not fouling both plugs up when you come to restart it. Btw be prepared for Smoke if you use Diesel or ATF.

You may have to do this more than once, if this is the case try turning the engine backwards when putting the Fluid in to get the back of the Apex\'s.

It may also be worth your while pre mixing the fuel (Add 2 stroke oil) The oil burns more cleanly and the more lube the better

[s00045732]

your a gentle man Grizzly thank you!

[Grizzly]

I forgot to say, getting anything into the plug holes is a bit tricky, best getting a lenth of rubber hose stuff that into the plug hole and pour it in that way. (Just don\'t forget to pull it out when you turn the engine over)