bsumpter

Hey everyone!

I have a YS45 that is around 10 or 11 years old. It hadn't seen much runtime until the last year or so, and is in great shape.

I had been running the engine with the stock YS muffler, and was pleased with it's performance. I've been craving more lately, however so I ordered a Macs header and 7.5cc tuned pipe. I set it up according to the instructions, but I still have a few questions. First off, some RPM readings (15% Cool Power / 11x6 APC Prop):

Open Face: 11,500
Stock Muffler: 10,800
Tuned Pipe: 13,800

I got a marked improvement with the tuned pipe, but now my needle settings are a little confusing. If I richen the mixture (using the needle valve), I can squeeze more RPM out of it WOT -- around 14,500. It runs great wide open at this richer setting. After idling for a bit, however it loads up and doesn't want to come on the pipe easily. The only way I can get the throttle response to be crispy again is to lean the needle out 6 clicks, and this leaves me with the 13,800 WOT figure.

The reason I'm confused is richening the needle is netting me more RPM when WOT. I'm concerned that by leaning it out to prevent the loadup at idle that I may be running her too lean. It's been my experience in the past that once you lean to the point you are losing RPM, then I've gone too far. This does not seem to be the case with the tuned pipe on there.

Is this normal behavior for a tuned pipe?

azhar

My Feedback: (19)

Hi,

Sounds like your low end may be a little rich. Try leaning it out some by adjusting the regulator screw. Do it a small bit at a time.

Azhar

bdtsr

My Feedback: (5)

As Azhar said, adjust the regulator screw on the bottom of the motor. DO NOT run your motor lean on the top end! Synthetic fuel will not provide enough lube and you will do damage to the motor. My YS .45 fs has seen 3+ years of hard running, it runs better now then when I got it (very light use). Turns an APC 11X6 @12000+ on a Mac's muffler (black one). Extremely reliable engine. Change the plug (OS#8) every year and forget about it!

bsumpter

Thanks for the tips, guys!

Yeah, I knew it was bad when I had to lean it more than it liked which is why I wanted to double check on here. I have been searching threads for the last hour or so, and I found some info from someone with a similar problem when installing the tuned pipe. He reported his problems went away when he shortened the header a bit more, so I just cut another 1/2" off mine. Using Mac's recommended method for measuring the header, I'm now at 4.5".

I haven't ran it yet with the new length, and won't be able to until tomorrow. I hope this solves the problem with the midrange as I've had this engine a long time and don't want to screw it up now.

My regulator is flush with the bottom of the housing, which I assume should be close to correct. Quick question: everyone recommends running the regulator screw flush with the bottom, but do they mean flush from the top of the screw, or flush from the bottom of the bevel? I know this sounds confusing, but those with the YS engines will know what I'm talking about. The screw is beveled inward, and I never really knew if flush meant "truly flush" from the top of the screw.

Thanks again, and I'll report the results again tomorrow.

BTW -- Is anyone familiar with the YS45, Macs standard pipe, and 11x6 APC combo? Just curious if my header length is in the ballpark.

azhar

My Feedback: (19)

Hi again,

Flush (from the top of the screw) to the housing is a good starting point. Most YSs runs great that way. Occasionally you will have some that just needs to be tweaked just a little.

My combo was a macs pipe with an APC 12x8 @ 12800rpm on 20/20 fuel.

Azhar

jon595

My Feedback: (2)

I had a YS 45 that I bought in 85, along with a Hatori muffled tuned pipe. When I got around to using it (1999) it would not run right. I was chasing the mixture, kind of what you are experiencing now, and the engine would die in the air. WEas about ready to give up when I saw a flier (Tony Stillman) who was using the same setup and he turned me on to an Enya #5 plug (cold). This transformed the engine into the most reliable one in my fleet. If all else fails......

bsumpter

OK guys, I've ran it with the shortened header.

The problem is still there. I have to lean the engine too much to get it on the pipe. If I richen it to where it runs max RPM WOT, then it is too rich to come on the pipe from idle.

I turned the regulator screw in a total of about 1/2 turn (1/8 turn increments), and it did help some but didn't totally solve the issue. I've also noticed today that the exahust residue is a dark black -- a good sign that I'm too lean. The motor is also hotter than I'd like after a run.

So I defer to your suggestions. Should I shorten the header further, or lean the low end even more? This problem only came about once I had the tuned pipe installed -- it never exhibited these symptoms with the stock YS muffler installed. I'm hoping it's as simple as me having the header too long and further cutting will alleviate the problem.

Oh, and the black residue thing -- I put some of it on a paper towel, and I didn't see any metal shavings at all. It appeared to be pure carbon. Is it possible that the tuned pipe is getting hot enough to "cook" the oil causing the dark residue? Or is it almost a sure thing that I'm way too lean and damaging my engine?

All suggestions will be appreciated. I have a demo flight for a local handicapped center coming up on Wednesday, and would like to have this resolved before then. I don't think I want to run it this way until I'm sure that I'm not damaging my engine.

Thanks!

Brian

bsumpter

jon595: I tried three different plugs in it today with no change. I did notice with the colder plugs it tended to start a little easier, but it did not solve my lean / pipe issues.

ewspears

My Feedback: (12)

Hi,
I can't bear to listen to this thread any longer! Never- Ever Run the engine at wide open throttle leaner than peak RPM!!!!!!
The YS ABC Piston/Liner is the most bulletproof I know of but even they have limits. You'd have already destroyed most other engines.

Quit Cutting the Pipe until you get the carburetion sorted out. Too long of a pipe won't cause carburetion problems. Too short pipe length can cause carburetion problems.

Work on the Problem, (too rich at low speed) Turn the regulator screw in till it is no longer to rich. If that takes 1 1/2 turns, so be it! If you can't get it to lean out properly within 2 turns; take the regulator apart to find out what is wrong with it.

bsumpter

Hehe .... so now that I've got your attention ......

There were no carburetion problems until I added the pipe. I've flown this engine in the UltraStick for a couple of years now with the stock muffler and it has been the most reliable engine I own.

Adding the pipe at full length DID change the carburetion of the engine. Thats why I assumed it was the header length and began chopping it off. No other variables had changed except the addition of the pipe, and yet the low end was now horribly rich. I still haven't cut much from the header -- it's at 4.5" using the Mac's method of measurement. I can add roughly 1/2" back to the length by pulling the pipe out in the coupler, which puts it at 5" length. But even at the extended length, the problem is still there. This is what is leading me to believe it needs to be even shorter.

Just for kicks yesterday, I installed the stock muffler again. All problems went away. I was no longer rich on the low end, and could adjust the top end properly (lean to max RPM, and richen until it drops about 300 RPM). With needles adjusted, I reinstalled the pipe and the problems returned.

I don't know for sure if I would call it too "rich" on the low side. Perhaps I just don't know how to explain it. I guess the simplest way to convey what it is doing is that it won't "come on the pipe" with needles adjusted properly. I have to go leaner, which I know I cannot do.

My brain hurts.....

I appreciate all the tips so far.

DarZeelon

Bsumpter,

If you have to lean the high speed mixture to get the engine on-the-pipe and then you must enrich it for consistent, safe running, your tuned system is too short.

This means the engine cannot get on-the-pipe at rich, two-stroke mixture, which becomes the correct mixture setting, once the engine is boosted by the tuned-pipe.

Changing the system length is not done only by cutting the header. You have to move the pipe forward, to within 1mm off the header's rear tip.
In this case you have to lengthen the system, by using a longer coupler (or a longer header). This engine is typically propped with a 10x6, or a 10x7, which are much less of a load than your 11x6. So you need more tuned length, not less.

The tuned length is measured from the piston/exhaust port to the widest point in the pipe, through the header and coupler.

You can know the length is right, if the engine gets on-the-pipe, as soon as the throttle is opened and opening the high speed needle causes RPM to decline; not to increase.

If it increases, your next, damaging lean-run is just around the corner...

Loading up at idle (or anywhere below 75% throttle), has NOTHING to do with the high speed needle. Only a mal-adjusted idle needle, or a mal-adjusted regulator screw in YS engines, can be the culprit. It is too rich with the pipe.

If you adjust the idle mixture using the high speed needle, your engine will idle, until you open the throttle and it dies.

Sincerely,

ewspears

My Feedback: (12)

"There were no carburetion problems until I added the pipe. I've flown this engine in the UltraStick for a couple of years now with the stock muffler and it has been the most reliable engine I own. "

All this statement means to me is that adding a pipe changes the carburetion requirements (it almost always does) and you have yet to meet those new requirements.

If you'll follow my origional post engine will run fine with pipe.

bsumpter

Guys, thanks for all the help. I'm well on my way to getting this issue closed right now.

The header pipe was indeed too short. I picked up a foot of silicon coupling material and some 3/4" aluminum pipe and put the header at 7" (from the factory it was 6", I was running at 4.5"). Now the carb tunes like it is supposed to, and it has no problems getting on the pipe. I can actually run her slightly rich now without any issues. Exhaust residue is now completely clear.

I'm going to start tweaking the length to see where it needs to be, but I know not to go below 6". I hope to have this resolved within the hour.

Thanks for all your help!!!

Brian