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Old 01-02-2006, 02:00 AM   #1
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pro engine builders help plz

hi i am having alot of trouble with my sh engine and it is seemingly never running properly by that i mean efficiantly to consistantly keep going without stalling for a full tank or 2 just continous running i cant get it too do it so i am considering pulling it apart and re putting it together so i can see the inside(what should i look for). and how could i air tighten it and make it be better because i seem to be able to adjust it so it accelerates from stop to top end without bog or sputter but then it seems run too hot 360 degrees farenheit was max temp last run is that too hot?
i need some major help on getting this engine running consistantly maybe i could send it to an engine builder to sus it out and fix it and then i can tune from his settings and advice from there?
any advice here i am experiencing so much trouble with this engine though i am a nitro newbie so time and experience is what i need but need good direction in doing so, so any advice is much welcomed and appreciated thankyou ...............regards............................ .........................Aaron.
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Old 01-02-2006, 07:21 AM   #2
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You could always send it to me! A local company (DSM Mods) that I work with does a great job with the local guys engines. If you want to take the engine apart yourself, I can give you a step-by-step if you want.......

It might be that the buy you bought the engine tried to take it apart and when re-assembling it, forgot to put a gasket on here and there, or forgot to reinstall head shims, etc..........
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Old 01-02-2006, 08:50 AM   #3
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What size engine do you have? When you pull it off of your vehicle check a few simple things first....

-Check to see if your drivetrain is binding anywhere.....
-Check to see if your clutch is functioning properly..... a broken clutch spring or sticking clutch shoe can cause some of the same problems you discribe....
-Check all of your fuel lines and fuel tank for leaks.....
-Make sure your pressure return line isn't too long or too short......(probably between 6-8 inches is about right for most engines.....


If all that checks out then it's time to check your engine.....

-First when you take the pipe and header off spray some nitro cleaner into the stinger with the other open end draining into a cup, check for metal shavings.... it's a simple step that most guys don't even think about, you can get a general idea of the condition of your engine without taking it apart.... If there are shavings then you know it could be expensive....

Most likely your problems stem from an air leak of some sort.

Cecking the carb-
- pull the carb off carefully
-is the o-ring at the base of the carb torn or knicked?
-was the carb body deformed by the holddown pin??
-you can use a small bead of automotive silicone around the base of the carb to seal it up, make sure all nitro fuel and oil residue has been cleaned from the mating surfaces.

Check the backplate-
- remove the pullstart (if you have one) and check for oil seepage into the pullstart case
- Remove the backplate check for a missing, torn or damaged gasket around the packplate mating surface
-check for a damaged or knicked mating surface
-agian you can reseal the backplate with a small bead of silicone....

Check the headshims
-contact the engine manufacturer or dealer to see if you can find the recommended number and size of shims for your nitro content, order new ones before you do this step.......
- remove the 4-6 bolts that hold your head onto the engine
-carefully pull the head away from the block
-use a hobbyknife to carefully remove the headshims from the head (they usually stick)
-check and make sure you have enough shims and that they aren't damaged
-check that mating surfaces to see if they are damaged..... you CANNOT use automotive silicone to seal this area
-while your at it check the condition of your piston and sleeve before you put the engine back together


-replace the exhaust gasket with a brand new one before reinstalling the exhaust system



IF you use automotive silicone to seal up your engine make sure you don't use anything that is permanent, but is also rated for up to 400 degs., allow it to fully cure before triing to start your engine....


It's nothing you can't do yourself, Have fun and enjoy expanding your knowledge!!!!!!
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Old 01-02-2006, 11:38 AM   #4
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impact ....:expanding my knowledge is what i plan on doing as i am a newbie to this hobby (nitro that is) i used race electric but cant resist the might of nitro so yeah all help is welcomed and much appreciated as far as the head shims, or gaskets are concerned, i bent them a little out of flat shape when removing them will this hurt?
good idea on contacting the sh engine comp. i will do for shim sizes and #'s , i may just buy a gasket set for this engine, i may as well do it now as i do not know what the previous owner has done to it,or even if he broke it in properly
thanks for the advice and your concern very welcomed dont be shy

savage : where are you situated? i live in australia, if you lived in aussie land then maybe an idea to send it to you, but postage to say america i am guessing you are, would be a fuss i think i probably would like to try it on my own for the experience if i make a mess of it then ill send it to ya.
you could probably take a look at my o.s max r.z engine its leaking fuel and stalls alot ,i would really like to get this going well but atm my sh in the xb8 is my priority so ill work on that first, then see if the os can be fixed if not i buy new eng for xb8 and put the sh in my practice buggy.
could i get a standard gasket kit for my eng at my lhs? i guess they would vary for dif engs.
im not quiet sure how to go about my clutch set up but ill check it out it helps alot to have u guys as pros help me out along the way, so, much appreciated from my point in r/c nitro racing.
i took the head off and the sleave out and the sleave has i little dark brown charcoal colour around the bevelled edge of the exhaust valve and its a little golden in colour on top of the piston (i left that in, just took the sleeve out).
what would be a standard maintenance be on these r/c nitro engines i mean you have the standard priming and oiling on starting and finish with using it but a maintenance of pulling it apart what would be involved in a typical pull down,and replaced?
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Old 01-02-2006, 02:19 PM   #5
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I would say unless you are racing at the very top teir then teardowns would probably be limited to when something goes wrong...just like the engine in your transportation car...

If the head shim is bent and not allowing a good seal then that could be all of your problems.... I would replace it and then see what happens.... I would also only only use a seal kit from the origional manufacturer.... unless you have proof that the kit will work exactly as the OEM parts.....
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Old 01-02-2006, 02:36 PM   #6
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Downunder, I'm over in the US but if you want any of your engines worked on, I pay for return postage. You can get replacement gaskets, look for gaskets for a SH .21, SportWerks Mach .21. they are the same engines. I could probably find gaskets over here than you could in australia, just because RC stuff is cheaper and more plentiful here.

Generally, when you tear down an engine, you will either pinch or replace the piston sleeve assembly. Pinching consists of taking the sleeve and slightly squeezing the top of it to create a tighter "pinch" between the piston/sleeve.

The easiest and cheapest method to get more "pinch" out of the motor is to take a pipe cutter (a copper cutter like you would find at a hardware store) and run the blades around the lower oil ring on the piston body a few times, and then test it in the sleeve. If you do it right, it will recompress the engine and prolong the life. I have "cut" my JP stock motors 4-5 times before they were done for and I have been able to get 14-15 gallons of consistent power from a "cut" motor.

Other than that, the only thing I would check is the crank bearings. They leak from time to time, and need to be replaced.
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Old 01-02-2006, 08:14 PM   #7
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Quote:
Originally Posted by SavageSYNTH25
The easiest and cheapest method to get more "pinch" out of the motor is to take a pipe cutter (a copper cutter like you would find at a hardware store) and run the blades around the lower oil ring on the piston body a few times, and then test it in the sleeve. If you do it right, it will recompress the engine and prolong the life. I have "cut" my JP stock motors 4-5 times before they were done for and I have been able to get 14-15 gallons of consistent power from a "cut" motor.
Can't say I've ever heard of this method. Would you care to explain to us how this would actually increase the pinch of the engine? I would seems to me that just going around the oil cut in the piston wouldn't do anything, unless it pushes a bit of aluminum out for a tighter fit.
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Old 01-02-2006, 08:35 PM   #8
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Making the oil ring deeper pushes the outer part of the piston above the ring out .5-2 mm, depending on how tight you want it. Basically, it squeezes the middle of the piston so the top fits tighter in the sleeve. I have seen many people do this and I do it myself, and I have to say that it works very well.
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