siwoodster

Hi everybody,

I’m just about at my wits end with my hyper 8 and it's overheating problem. Its got the bog standard Mac28 engine in it running on 20% Tornado fuel, its had about 15 litres through it and has given me hours of reliable fun since I got it about 6 months ago. My problem is as follows (I'll try to keep it short ) : it starts, idles and runs fine from cold, but after about 1 tank with very few WOT runs(sometimes less) the engine revs start to take a second or two to return to idle and are hunting up and down when they do until a few minutes later they don't settle down to idle at all and the engine just doesn't sound right, kind of a high pitched whiney sound, its at this point where the temps start to rocket up too, suggesting an air leak:helpsmilie: Next I tried spraying wd40 over every susceptible leak point to see if the revs dropped back down to highlight a possible leak but nothing happened wherever I sprayed. I have had the carb off and removed both the hsn and lsn needles and the o rings look fine, refitted it all and bubble tested the carb under water, no leaks at all. Next I removed the pull start and back plate and added some instant gasket sealer, and whilst I was there, put some sealer around where the carb meets crank case and the pinch bolt too but still the same happens.

One interesting thing I noticed when I took the pull start off was quite a lot of oily residue on the pull start side of the back plate, don’t know if this is normal or not? With the pull start off and back plate still on (i.e. no seals or o rings disturbed yet) I can see the con rod thru the round hole in the back plate, so how is this air/gas tight when the pull start goes back on as it doesn't have any gaskets or seals against the back plate?


I’m still quite a newbie to nitro but what I have learned from this and other forums, I have had a hell of a lot of fun putting into practice but I really am stuffed on this one I’m hoping someone on this great forum can point me in the right direction, as I’m reluctant to give in and take it to my lhs to fix, I’d much rather have the satisfaction of doing it myself

Is it safe to leak test the entire engine under water? Obviously I want to avoid getting water inside the engine, but do I need to remove the pull start or anything else first?

Any suggestions on this would be greatly appreciated as what little hair ive got left is gonna turn grey soon if I can't sort it

rchertz

gota be honest torn fuel aint the best,it mite not be the cause of high temps tho,
have you tryed goin back to base settings?
also keep the lsn rich an see how it goes,
also is tickover ok?
if its hunting its to lean,,
hope this helps
ps,wat temps is it hitting?

j_blaze

are you using the in-line fuel filter? check it for bubbles inside the line when you go wot on the starter box. i've had it happen before and it did it again before a club race on my rb s3, it normally ran at 206ish and that day it hit 351, after all sorts of tuning changes it barely got under 300 but lost all tunability. i had a small leak from the front bearing, changed it out and it was still hot. then i noticed the fuel filter leak, all good now.

Vigilante212

Could be a bearing leak.

adz06

mach 28 engine is [:'(] do a search i used to use the hyper 8 rtr mach 28 after i hit 2 gallons it would not hold a tune would constantly over heat half way through a tank found a cabr leak i fixed it still had the same problem checked every where else could not get it to run right so i sold it on ebay as "spares" and picked up a hyper 21 8 port for £30 new.

Jerzferno

Siwoodster, I vote bearing leak also. I had the same symptoms with my Kyosho GXR .28. I did all you did and then some. After you run, do you have a lot of oily/fuel between the flywheel and engine block? Do you have a stripe of fuel on the inside of your body over and around the flywheel? If you dont, that doesnt mean you do not have a leak. Those symptoms of mine were from an excessive leak. I really believe thats the problem. Your story sounds exactly like mine.

supertool28

My Feedback: (2)

You have a air leak. If your getting oil coming out then air is going in. Fix the leak and your engine will run good again. If your not sure how to fix it then take it to your local hobby shop and they should be able to help.

rican25

I will fix this as quick as I can..... ready?..... THROW IT OUT!!!!
honest to god I wish I never saw that engine, I had the most trouble out of that thing! I was and still am pretty new to the hobby so it was frustrating to say the least. I even had a guy that knows his way around these things tune it and he couldnt figure the thing out. Search this engine on here and you will find you are not alone!! I call mine the Crap-Star .28!! shine it up and use it as a paper weight!! all that see it wont believe its an actual engine. well.... its kinda not but the idea is given! I now have an Axial in mine and absolutely love the thing!

martrix

Only way to fix it permanently is to toss those garbage pull-starts. The engine is scavenging extra air from the worn bushing in the pull start shaft and the engine is running lean, no matter how much you richen the engine. The only other option is to find a pull start that has a bearing with a tight seal (same as clutch side)as the go-between/seal from the crank-case to the pull start shaft, and I don't think anyone makes them.

Sportwerks #SWK8057 back plate should fit your engine to convert it to bump start. (I think)

adam-69

i garantee i know the problem..its a mach .28 .
i have ran many of them, all liked to run at around 280 degrees.

siwoodster

Hi all,

Just a bit of an update. I found an air leak from the pinch bolt that secures the carb to the engine, the bolt was tight but still leaked quite a lot. I put some instant gasket on it-leak sorted! With this now done I filled her up and went for a test drive. The engine was much much better but the hunting idle and high temps came back after about 1.5 tanks[&o]
I richend the lsn bit by bit untill slowly the idle came down and sounded normal again. It now runs sweet as a nut, ive just come back from giving it a good thrashing (about 6 tanks full one after the other) with 4 wheel power slides, wot runs and donuts galore and not a single stutter or high temp in sight! I`m happy now, very happy!!
Thanks to everyone for your replys, especially the one about richening the lsn............job done cheers!