associatedrules

Hi everyone, I am new to the large scale world and just purchased a Shenqi (Firehammer MT knock off). I have owned it for a little over 2 weeks so far and cannot keep it running. I know most people are going to reply with "you get what you pay for", but I just really wanted a 5th scale and couldn't afford an FG or HPI. Basically the problem I am having is chasing the idle and low speed tuning. It runs great past half throttle, but after letting off it will either bog down and die or keep a high rev and idle around the yard at like 5-10mph. I initially thought it was an airleak on the carb/intake, so yesterday I took the intake apart and used Permatex Form-A Gasket sealant on it. This helped slightly, but it is still being very inconsistent on it's tune. The thing that gets me is that I wanted a 5th scale so badly, because I though they were more reliable than nitro. So far it is becoming more of a pain then the nitros. The engine it has in it is supposedly a CY23 and in the manual it even calls it a "Fuelie", but I do not hear these problems coming from HPI owners. Any advise would really be appreciated. If it will help you help me I can try and post a video with audio tomorrow, just let me know. Also if I post a vid please don't make fun of the attempted repair job of the body mounts!

bentley marshall

did you oil the air filter befor you used the truck ?? if not the engine is more than likely full of crap

or if thats ok

i would check your head gasket soulds like a air leak of some sort if you can get it to run again and spray crc wd40 round the base of the head see it the engine changes tone or dies it wil be the head gasket

allso make sure your pulse ports arnt blocked in any way going to your carb

associatedrules

I did oil the crappy filter it came with, but am afraid that some sand may have got through. If so do I need a new engine? Also what is a pulse port?

bentley marshall

if sand has got in there you might need a rebuild

the pulse port is a small hole that give a pulse to the carb to pump the gas up to the carb

take ya carb off and you will see a small hole in the carb block and in the gaskets make sure they are all cler and line up

associatedrules

Will do thanks very much for the help! If any dirt got through I am looking at some engines on Daves and also rebuild kits. What would you recommend? Also I am waiting on an airfilter and Outerwears cover from them also. So if I do get a new one, the same problem will not reoccur.

bentley marshall

yeah a good air filter is a must and keep it well oiled i use motor cycle filter oil its sticky messy stuff but works well

splcrazy

the bog and the irregular idle you mention is caused from bad carb needle tuning . your idle should not be turned in too much its better to have the idle screw turned out just a tad more than recomended , and the high and low needles need to be turned out at about the same half way in the middle.

associatedrules

I have messed with the tune quite a bit now. I have reverted back to factory setting about 4-5 times now. I am not absolutely new to tuning engines, just new to the gasoline engines. I will start to think that I have it tuned in good and it will idle and take off fine, but after a few laps around my backyard track, it all goes sour. The engine will start idling high, and sounding lean. Then I punch the gas and it bogs down and goes back to high idle. I will then hall butt around the track out of frustration, and I mean wide open insanity not caring if I hit anything at this point. Bring it back in and it idles fine for awhile. Take back off driving like a mad man again thinking it likes it, and when I let off it either dies or idles high again. This is with a lot of different tunes attempted on the needles and all end with the same results. I started out making the recommended very tiny 16th of a turn increments, and after much frustration of no difference have even tried a quarter turn increment with no real notice of difference in result. The plug looks used but I wouldn't necessarily say bad looking. I will just disassemble the motor in the morning and see if it is in fact damaged. Again thanks for all the help! I just wish I would have saved the extra money for something better...maybe a 90's model Eclipse with 80,000 miles on it from a friend of mine. Could have made a full scale RC.

da mad maori

start the engine and spray wd40 around all the joins.... if the idle changes drastically when you spray a certain area, then that where an air leak is......

failing that;

tear the engine down and check everything, bearings, gaskets, check the piston is loose in the groove...
you say the sealant helped??? then it must be an airleak somewhere

cyclops1970

My Feedback: (5)

here this is copy'd from DDM's support page for you ..
How should I adjust the jets on a Walbro Carburetor (WA-167 / WT-603 / WT-668 / WT-257 / WT-813, etc)?
These carburetors require regular adjustment to ensure peak performance, and also to avoid an unsafe lean condition, which can prematurely damage your engine. If you find your top-end RPM's have fallen off a bit, or if you experience lagging or surging, it is probably time to re-adjust the carb jets. To ensure max performance and engine life, follow this procedure:
1) Locate the low and high RPM jets on the side of the carb - they are usually marked with a L and a H. Turn both jets completely CLOCKWISE ( to the fully closed position).
2) Rotate the Low jet counter-clockwise to 1 and 1/4 turns open.
3) Rotate the High jet counter-clockwise to approx 1 and 3/8 turns open.
4) Now, start the engine. You may need to turn the Low jet slightly one way or the other for the engine to start.
5) Adjust the Low jet as desired until the idle is where you like it. Turning clockwise ("CLOSING" THE JET) will produce a higher idle, and counterclockwise ("OPENING" THE JET) will produce a lower idle (and eventually flood and the engine will kill, if you turn it too far).
6) Open the throttle lever to full blast. Adjust the High jet until you get maximum RPMs. Note: this will probably be REALLY LOUD. Listen for the highest-pitched whine to tell you where max RPMs are hit. AFTER YOU FIND THE MAX RPM SETTING, TURN THE HIGH JET COUNTER-CLOCKWISE ("OPEN" THE JET) APPROX 1/16TH OF A TURN TO ENSURE YOU HAVE SUFFICIENT GAS/OIL MIX TO COOL THE ENGINE PROPERLY.

Note: The above are just general guidelines. You may need to adjust both the H and L screws once you begin driving, depending on engine loading, altitude, humidity, etc. The trick is to find settings that work well for you, and stick with them.

Here is some helpful information regarding common carburetor tuning problems:

If your engine stutters at full throttle and cannot reach full RPMs:
The high jet is too far open. Close the jet by turning it clockwise slightly, and then ride-test. If no improvement, repeat until desired results are achieved. Once you have found a workable setting, open the jet approx 1/16 of a turn to ensure sufficient fuel/air mix.

If your engine bogs out when transitioning from low speed:
The high jet is too far closed. Open the jet by turning it counterclockwise until you are at least 1 1/2 turns open, and then gradually close the jet until performance is as desired. Poor engine compression, blocked exhausts, and very heavy engine loading can all also cause bogging.

If your engine idles very fast and kills if you attempt to slow the idle:
You may have an air leak in your intake. An easy way to check for leaks is to spray the intake manifold and area surrounding it with WD-40. If the idle changes after you spray the WD-40, there is an air leak. Common areas for leaks are between the manifold and the cylinder, and between the carb and the intake manifold. Inspect the manifold, carb gasket, and intake gasket for cracks or other signs of damage, and replace if necessary.

If your engine idles but then slowly kills:
Your low jet is too far open. Close the low jet by turning it clockwise until a stable idle is achieved.

speedy.d

i had similar problems with my original fs motor, i got tired of the erratic behavior (i think the engine was made from swiss cheese) so i pulled it out put in the ol'28.5 cy and now she runs great.

i just put a 26 head kit on my buddies fhmt he also is running a jetpro. this little bit of increase in displacement turned it into a wheely monster. a good air filter, filter oil, and an outerwears cover is your best bet on keeping crap out of your motor.

SAVAGEJIM

Well, Shenqi , like you said, is a clone of a clone (because Smartech cloned the FG to make the Firehammer for Duratrax, Duratrax has yet to make any of their own RCs).
And that reaises the question about the engine too. Is that a real Chang Yang (CY)? or is that engine a clone of the CY and they just put the CY stickers on it?
Personally, I dont trust it, and I would think they didnt clone the CY engine very well, especially in the carb department (as so many other have already mentioned before me).
What I suggest is that you take off the crappy-sorry clone carb from this proported to be "CY" and inspect that carb thoroughly, measure it up, and see if a genuine Walbro Carb will fit. That way, by going with genuine Walbro, you elimitated your carb problem.

Furthermore, whenever you can, I strongly suggest you buy a brand new genuine CY, or if you can spare about $75 more, get a genuine Zenoah. I cannot help but suspect that Shenqi is pulling the wool over your eye and put a fake CY into your RC instaed of using a real CY. Though a CY is not a Zenoah, a CY does NOT have that much problems with tuning. They are reliable engines for what they cost.

speedy.d

savagejim is very knowledgable on such matters, the man is like a walking encyclopedia!take his word it is worth its weight in gold. the reasons he has listed are why i changed my motor to cy. it will save a ton of headaches. a good motor will idle thru an entire tank .

associatedrules

Thanks for the very helpful advise guys. I have a CY head kit on the way, so hope I didn't waste money on it. I will go a head and measure the carp out and find a Walbro to work. Shoot maybe it will be better to just get a CY23 now from Daves for 149 and put the 26 head kit I bought on it.

associatedrules

I think I found something. I took the low needle out and found that the o-ring looks damaged. Would this cause the problem? It must have been over tightened at the factory.

SAVAGEJIM

Definitely! take off the old o-ring, bring it with you to the local RC store, and try you best to find one with the very same diameters. A ripped/torn or warped o-ring in the carb can leak LOTS of air.

If you can find an equivalent sized O-ring at the store, while you are there, go pick up some Associated Green Slime as well. When you get home, wipe a small dab of Green Slime on the new o-ring (and even the other O-rings on the needle if there are more rings) and then slip the new o-ring onto the needle. Then, reinstall the needle.

What Green Slime does is lube up the o-ring to go in smoothly without damaging the o-ring and also, it even helps seal the needle threads and the needle hole against air leaks.

mooman007uk

If you end up needing a new (about a tank thru)668B walbro carb pm me I just bought an 813 for my rampage so got one spare

associatedrules

Yep, that was the problem. I didn't have an o-ring that size, so I just put a tiny bit of grease on it and it fired up and idled fine. Now to either find a new o-ring or get a better carb.

associatedrules

Another question, would a tuned pipe make it easier to tune the engine in? I figure a 2 stroke really needs a pipe to run right, since it needs correct back pressure to run right. Also, do the silenced pipes work as good as the regular pipes?

splcrazy

from what ive tested silenced pipes restrict power quite a bit , i prefer an UNsilenced pipe everytime , anything other than the stock can muffler is going to better , as for tuning with differant pipes its about the same , if you have good hearing you can notice audible differances when tuning with differant pipes

SAVAGEJIM

A tuned pipe will help performance definitely. As for hurting idle? No, not really, you might hear a slight "hop" or "skip" like every 50 revolutions, but dont worry, it is not bad so long as your engine idles without stalling, sounding like absolute crap, or runs to fast such that your clutch starts to engage. Besides, tuned pipes are ment to provide their return pulses much higher in the RPM range, like 9K-10K + RPMs, where the meat of the engine's torque curve resides.

associatedrules

Thanks, you have been a great help with this. I just ordered a new 668 Walbro carb, Klotz oil, new fuel line, and gaskets from DDM. I will hold off on the pipe until I get it running correctly. Thanks all for the advise!

da mad maori

good stuff you found it told ya it was an airleak LOL

look on the crank case behind the flywheel it should have "chung yang" cast into the case... if it is then you have a CY which is a copy of a ZEN

associatedrules

Yep, you were spot on! Thanks for the help, and I will let everyone know how the new carb and head kit turns out. May wait until I get a pipe and steel pinion to install the new head kit though. Also looking at alloy engine mounts...this is getting to be addicting.

srt10

My Feedback: (20)

Great job finding the problem, looks like you got a good deal after all!
Let us all know how the new carb and head kit work out!