OS .21 max RZ Question

[R/Cnutts]

Hi I have this Os motor and it will not tune for the life of me. I am sort of new to nitro but I have several other nitro's and I've tuned them just fine.

My Os is on a Hyper 7 and well when It does run WOW it's fast. I can only get it to run sort of...when I have it extremely rich(spitting fuel from carb on idle) and it constantly looses it's fuel prime. I checked the tank for leaks. I also got it to run better when I disabled the expansion chamber but if I pic the buggy up by the wing it dies.....could the fuel lines be too short/small inside dia.?
Someone suggested to me that the piston/sleeve was worn out but it has as good if not better compression then the other 6 running nitro's I have. Are Os motors that finicky?

 

[cdcderby]

Os can be very much a pain. I've always had air leaks around the banjo fittings and the back plate on 5 of the 7 I have. I take o2 sensor safe gasket sealer and run a very thin bead around the banjo, base of the carb, and the back plate. After that retune and they work great. Hope this helps.

 

[R/Cnutts]

I will try That Thanks. And is it easier to tune with the expansion chamber blocked off first then reattach and tune more? or tune it complete?

 

[2revo1maxx]

Check the exhaust, check the o-rings and seals on the engine, and reset the needles to factory specs. O.s. engines are easier to tune than most engines, so you need to look for cracks and leaks anywhere on the engine.
How much fuel has been run through it?

---------- Post added at 8:34 AM ---------- Previous post was at 8:33 AM ----------

Has the engine been apart?

 

[R/Cnutts]

I picked this buggy up 2nd hand so I have no idea how much fuel has been run through it. It has fairly good compression and crank case vacuum.

I removed it and while blowing through the fuel inlet found several leaks(chamber on backplate,expansion fitting under carb, banjo fitting for carb) I've sealed those up and i can get it to run 1-2min at a time but I just can't get it rite. I have an OFNA .21 3port on my other hyper7 and I upgraded my T-Maxx to a OFNA .21 4port they both scream. I set the OS to those settings to start with but what is OS .21 max rz factory settings? I've been using 3-3.5 for hsn and 2-2.5 for lsn. also I don't even start to tune until engine is at least 160*temp and on a 1/2tank fuel.
Exhaust is good both grommets are new and springs are firm.

 

[cdcderby]

High speed needle should be at 3 full turns from closed and low speed should be one full turn in from flush w/housing, Look down the top of the carb and make sure there is .5 mm opening form closed. That is the base line from new if I was broken in rite you should be able to start leaning Hp needle quite a bit. I have found it's best to tune at full temp and final tune temp should be between 230 and 250.

 

[R/Cnutts]

ok thanks I'll try that

 

[2revo1maxx]

Just keep in mind what temperature it is outside. You may have to run more than 3 turns if it's cold out.
230-250 is a good temp range to shoot for, but is no way to tell if an engine is tuned properly.

 

[R/Cnutts]

It still isn't rite so I think I'll just rebuild it and then i know what I got. Thanks for the help

 

[cdcderby]

I've had engine (os) that seemed to have good compression when they are cold but no compression once they warm up. OS isn't a true ABC piston and sleeve,They are ABN so the sleeve tends to expand faster than the piston when they get hot. I'd see if there's an after market piston and sleeve that's a true ABC.

 

[R/Cnutts]

Maybe?

I just found 1 broken spring in the clutch...could that be pulling enough drag on the engine to require the massive amounts of fuel and such a high setting on my idle just to make it run?

and the abc piston is a good idea i will look in to that. however I don't seem to feel a difference in compression from cold to after run....by hand...that does make a lot of sense

UPDATE
Went through the clutch and lsn is at 3.125(half turns) and high is 6.5 Runs great Incredible power through entire throttle range and it will idle for about 2min on its before it stalls so its progress but under extreme braking from Wot it stalls and I have to have the Idle screw at max..... Am i getting closer?

 

[2revo1maxx]

A bad clutch can cause trouble. I wouldn't worry about the piston and sleeve being abn, if that's true in the first place.

 

[cdcderby]

Yes it's true Os is made in japan were it's illegal to chrome plate. But A bad clutch spring would mess with it alot.

 

[deckman]

If you are increasing your idle gap than I
Would say your lsn is still too rich. I always
Set my idle gap around .05-.08 and tune my
Lsn. Once my idle gap is set I never touch it
Again. I just fine tune the lsn. Sometimes I
Richen it up a hair and sometimes I'll lean it out
Depends on the weather conditions.

 

[R/Cnutts]

the clutch i just used parts laying around i was thinking that the springs might be week and on idle they are trying to engage. witch the more they try to engage the more idle speed i need.....am i thinking rite on that?

 

[cdcderby]

Yes you are. Raise it and see if the clutch engages on an idle. Also check your bearings. If you have sticky or bad bearings you'll have the same issues.

 

[R/Cnutts]

Yup I believe that was a lot of it. Now I'm waiting on parts. I figured this would be a good time to upgrade to billet clutches while I was at it. Let you all know how it foes after new parts. Ty

 

[R/Cnutts]

WOW...ummm...Thanks for the help guys but well I got it running like a top and my guess is there was a hairline crack in the conrod.....massive failure...busted con-rod/shattered piston/belled the bottom of the sleeve to the point were it will need to be cut out/bent the crank...so its same to say it's dead...Oh well rite. Thanks Guys.

anyone got a good deal on a big block?

 

[cdcderby]

Amain hobbies. Go engine .21 5+2 port. Great engine.

 

[R/Cnutts]

how much you asking?