Getting frustrated on tuning

[NvNitro]

Hey guys, I'm hoping you can help here. I got the new mammoth st with the 24.7 mill. This is what's going on. I get her started and running at around 180 and she shuts down when I go to give it the gas. In the past I had it up to 220 on breakin when I broke the pull start. I replaced that from then on its been messing with me. I checked for air leaks on the back plate, carb, and tank..all good. At one point I put everything back to factory settings, and then started to lean out hsn and she is shutting down at about 180. I'm getting frustrated here. It needs to be broken in about another 2 tanks 290cc tank at 230, but can't get there. What am I missing here? Throw out anything at this point!

SD..can you come home early from vacation for a brother..lol

 

[Monkey Wrench]

First thing that comes to my mind is setting the HSN to factory, leanng the LSN about an 8th of a turn and trying a new glow plug. Judging by what you have posted, it sounds to me to be a bit fat on the low end.

 

[jon2]

Just for break in why don't you increase your Idle a bit so it will idle a bit more to keep it running. Mind you to keep it running rich till break in is done.

Have you started using the Starter box you ordered?

 

[NvNitro]

This is whats got me puzzeled. The idle is pretty high already (not been touched) almost to the point of ingaugeing the clutch. Got to do some hacking on the starter box. MW put a new glow plug in this morning.

 

[jon2]

Have you sealed the engine yet?

 

[kx250ryder]

You should be able to make your motor hit 300 degrees F or more (not that its a good thing, but it shouldn't be hard). If you are not able to get it into the 200-230 degrees F range, then you likely have your low speed needle extremely rich.

To test, get your car warmed up, then pinch and hold the fuel line until the car dies. This should occur between 5-7 seconds from when you pinched it. If it takes longer, lean the low speed needle, if it takes less time (not likely for the temps you mentioned) richen the low speed needle.

EDIT: Once the engine is broken in, go for 230-250 degrees, with a pinch of 3-5 seconds, and idle as high as possible without making the car move. Make sure that you still see smoke visible between low to mid RPMs while accelerating.

 

[vbgagnon]

I agree with kx, it sounds as though your lsn is set too rich.

 

[kx250ryder]

A couple telltale signs that your needles are out of balance:

1.) Once chassis gets warm (heat saturated) the engine keeps gaining temperature (it should actually stabilize, but doesn't). Another symptom would be that the car dies when letting off the throttle from mid-high RPMs. That is typically lean High speed masked by rich low speed.

2.) Engine accelerates well at low RPM, or stalls instantly when lots of throttle applied at low RPM, but is running blubbery at mid-high RPM. Less common, but that is typically a lean LSN masked by an overly rich HSN.

 

[Plaidfish]

sometimes after running too rich on the botom for too long you can build up sludge (excess oil that didn't get hot enough to burn out of the engine or pipe).....sometimes you need to bite the bullet and rev it WOT for a second to clear that gunk out if you don't want to tear it down........

 

[NvNitro]

Thanks fellas, I kinda gotta sneeky feeling that my needles are in fact out of wack, buy all that is being said here. Because it does do the low rpm and accelerates well, and stalls when throttle is applied. At one point it was running fine at around 180 so I leaned out about 1/8 of a turn to get temps up and thats when it started stalling out on me.

Plaidfish- I know what your saying about the wot...but I want to see if I can get the needles back in line..if that's the problem

 

[digger]

I had mine out this weekend. It was doing the same thing. I had to lean out the lsn before it would rev up. Think I ended up about a quarter of a turn?

Mine was running good when I put it up last year though. Just broke in. Part of my re-tuning is due to the air filter being dirty. Didn't notice it till I got out. I know that isn't your problem but try leaning the low-speed a bit.

Are you keeping the 24/7 on yours?

 

[jon2]

Thanks fellas, I kinda gotta sneeky feeling that my needles are in fact out of wack, buy all that is being said here. Because it does do the low rpm and accelerates well, and stalls when throttle is applied. At one point it was running fine at around 180 so I leaned out about 1/8 of a turn to get temps up and thats when it started stalling out on me.

Plaidfish- I know what your saying about the wot...but I want to see if I can get the needles back in line..if that's the problem

Hey Bro,

I read that you leaned out the LSN an 1/8th of a turn. Did you adjust the HSN to compensate afterwards? I say this because now you are tuning the fine spray of fuel into your carb.If your HSN is too lean than you can still have problems. The overall flow is at the HSN but like it has been said the low end grunt is at the LSN where you accelerate. Let us know how you fare.

Also I am working on getting you pics...

 

[NvNitro]

I had mine out this weekend. It was doing the same thing. I had to lean out the lsn before it would rev up. Think I ended up about a quarter of a turn?

Mine was running good when I put it up last year though. Just broke in. Part of my re-tuning is due to the air filter being dirty. Didn't notice it till I got out. I know that isn't your problem but try leaning the low-speed a bit.

Are you keeping the 24/7 on yours?

Digger...I really like the 24.7 I think once I get the tuning issue worked out I will like it just fine. I just have this feeling that I'm way lean on the lsn, but when I put it back to factory settings...still does it. So that's why I am so confused.

 

[digger]

Factory settings are always pretty rich.
The way I got mine was just bumping the throttle. If it acted like it was going to die, then I leaned it out a bit. Kept doing that till it would rev up. It got better everytime.
Keep the glow starter on. It helps.

Mine still isn't tuned, but I hope to get it the next time.

Be patient.
Let me know how it goes. I'm keeping the 24/7 on mine. Got it in my X-term and have no complaints.

 

[NvNitro]

Well, I finally figured out the problem. My hsn was too lean, and my lsn was too rich. This I found out only because the guy at my lhs looked at it and readjusted it. Strange way too adjust but works awsome now. Running 230 all day long. He adjusted by taking the hsn screw all the way out, and the fuel line off carb and putting a separate line on the carb, then blew thru it and adjusted it by the pressure of air comming out of the hsn screw area. Weird.. Well, how ever strange or not it sure worked. I'm back in bussness. Run 1 more tank 290 cc and then start tweaking. Glad that nightmare is over. I tried asking him questions on how he does it, but he wouldn't give up his secret.

 

[jon2]

Well, I finally figured out the problem. My hsn was too lean, and my lsn was too rich. This I found out only because the guy at my lhs looked at it and readjusted it. Strange way too adjust but works awsome now. Running 230 all day long. He adjusted by taking the hsn screw all the way out, and the fuel line off carb and putting a separate line on the carb, then blew thru it and adjusted it by the pressure of air comming out of the hsn screw area. Weird.. Well, how ever strange or not it sure worked. I'm back in bussness. Run 1 more tank 290 cc and then start tweaking. Glad that nightmare is over. I tried asking him questions on how he does it, but he wouldn't give up his secret.

Sounds a bit familiar.... LOL. I am glad you got her running. When are you going to start jumping her?

 

[digger]

One of the guys at the field showed me that on my 4-stroke. But it was with the low speed needle. Said he opens it up till he can just start blowing through the carb?
I never tried it or understood it, but the engine fired right up.

Glad you got going. Nice to see a couple more guys on here with the ST's.
I may need help.

Good luck with it.

 

[NvNitro]

One of the guys at the field showed me that on my 4-stroke. But it was with the low speed needle. Said he opens it up till he can just start blowing through the carb?
I never tried it or understood it, but the engine fired right up.

Glad you got going. Nice to see a couple more guys on here with the ST's.
I may need help.

Good luck with it.

Ya..the weirdest thing. Like I said earlier I really like it, it was just pissing me off on the tuning. Let me know if I can help you anytime digger, I will do my best my friend. Hopefully we can hook up at the West Coast Bash thing if it comes thru. Like to put some more faces with the names.

ttyl