49mm Steel Sleeve --- She Rips!!

[Chainlube]

Absolutely. I intentionally buy the problem child engines because I love a challenge and a bit of adventure. I would take a well designed and tuned 49cc over this "110" (85cc) as it came out of the box and probably be faster.

I totally agree, my Auto-Mini with the 48cc was a fairly quick little bike with its 20" wheels and all.

 

[Chainlube]

Tiny bike.

 

[TheWizzerd]

This is just a hunch based off of your apparent knowledge and skill with the engines in question - I would say there is a port issue of some sort at work here. Either cross talk or crankcase bleed off and/or a blowdown or uneven transfer port timing issues... or any combination therein.

I say this because my iron sleeved 110cc engine, while a bit apples to oranges, had all sorts of port issues similar to what you describe. The piston blocking the exhaust port by about a third and terrible exhaust duration to incredibly small and uneven transfer timing and durations with piss poor blowdown. The only thing even remotely "good" on the entire thing was the intake side and I use that word loosely. If we pretend it had good compression and squish... which it didn't, it would have never made any meaningful power anyway.

I totally agree. That has to be the case. I found it a bit odd that after port matching the first sleeve to the jug and it performing poorly, then trying a new jug from a different more trustworthy supplier, and simply cleaning up the slag that performance it unchanged. So that led me to believe maybe a recent change/manufacturing issue.

I wanted to confirm others port maps to see if perhaps there has been a flub up recently in manufacturing that has the ports way off.

The 2 jugs are from the same factory. They have the little woodpecker logo cast into them both, and identical other than the CDH jug has a bit more sleeve overhang.

I tried all day today going back through the entire process of elimination with various components to try to eliminate myself as the problem. Only thing being constant is the bottom end, which is seemingly 100% OK. Not much to go wrong there other than a massive leak through crank seals, case gasket etc. , and case pressure seems OK.

No go. These 2 49mm steel sleeve jugs just will not perform.

I would at least expect a minimally noticeable difference between the port matched and decked one vs the "dirty" one. The fact there isnt seems to me that the ports are simply off, even in the aluminum jug casting so no amount of matching the sleeve to the casting is going to help.

I will degree the ports out on these as well.


Its a damn shame too as it runs smooth as silk on both jugs.

.......I too buy the problem child (or that needs some work) stuff. I am nobody if I dont have something to work on.

EDIT: .......BTW, The transfers are the same height. When I matched the first jug I made sure they were identical. Within .005" to be exact. On the second that I just cleaned up, they are within about .07in. Not perfect, but certainly doesnt account for the problem especially since a perfectly matched one performs the same.

 

[TheWizzerd]

I would like to add, some new guys with little or no experience see 100cc or 110cc and think bigger is better, not so.

I intentionally referred to it as the 49mm, rather than "100cc" specifically to the fact I am not one of those guys.... lol

But "better" in this case means this top end should theoretically, and based off some seemingly trustworthy users' experience offer a bit better low end. That's the only reason I am after it.

Low end aside, If I can get it to perform at least as good as a decent stock 47mm top end, and it remains as smooth on the low end as it is now (with what little power it does have now)...... it will be a keeper and I will continue to use them.

 

[Greg58]

I have another 49mm top end that I plan to use on my 38mm stroke engine, the problem will be the port timing, being a 38mm stroke it will have more piston blocking the ports at BDC, that engine needs a top end, it's 8 years old. The problem I've found is the older style cylinders have the port locations higher on the cylinder than the newer and now the G4 style. On all of the older style cylinders you had to trim the piston skirt to clear the intake port at TDC, now all cylinders I have found clear at TDC, since both top ends act the same have you checked the stroke of your bottom end? I have the one engine that is a 38mm stroke but uses a high pin piston, yours seems to be like mine.

 

[TheWizzerd]

I have another 49mm top end that I plan to use on my 38mm stroke engine, the problem will be the port timing, being a 38mm stroke it will have more piston blocking the ports at BDC, that engine needs a top end, it's 8 years old. The problem I've found is the older style cylinders have the port locations higher on the cylinder than the newer and now the G4 style. On all of the older style cylinders you had to trim the piston skirt to clear the intake port at TDC, now all cylinders I have found clear at TDC, since both top ends act the same have you checked the stroke of your bottom end? I have the one engine that is a 38mm stroke but uses a high pin piston, yours seems to be like mine.

Its 40mm stroke. Hence why the piston covers about 30% of the exh. port at TDC. Skirt is about 2mm into the int. port at TDC. This is with a single base gasket. With 2, those obviously move.

Today I decked the second jug, leaving the ports "dirty". Set squish at .8mm (using the head that I corrected), and its noticeably better, but still nowhere near an untouched decent 47mm.

The cleaned up jug, with squish set at .8mm does not have the same noticeable improvement.

So, I do indeed think its a combination of everything to do with these jugs. They just simply seem to be wrong and there isnt much you can do with them. Leaving it "dirty" is better, but matching the ports makes it worse, all else being essentially identical. The bores actually mic'd to within .001" of each other, so they are as close to identical as it gets other than the port sizes.

So on these jugs, it seems opening the ports up to match the casting screws up the port timings.

I will try widening the dirty ports, and leave their tops where they are. Improving flow without changing timing, and see where that gets me. If that shows a significant improvement, maybe some filler material (JB, PC7 etc.) to kill the lips around the sleeve is in order and improve the flow there.

 

[TheWizzerd]

OK.... I think I got her close.

I widened the sleeve ports to match the jug casting. Leaving the tops and bottoms of the sleeve ports as they were from factory....overhanging into casting ports. Running a single base gasket. There is about 2mm overhang on all ports. Which jives with the ~2mm deck over piston height.

MUCH better.

It now feels noticeably better on the low end than my "built" 47mm that's my typical driver. Feels about where I would expect it to be in this configuration. Haven't wound it out yet as its a new jug and rings.... but it seems like it wants to wind out now.

This is with the BoFeng carb, no reeds yet. I will drop the windowed piston and reed setup in, and get the pumper carb put on so I can tune the fuel delivery. After that I think it will meet my expectations. That being a a smoother, slightly more torquey low end.

So my conclusion is, on these recent steel sleeved jugs, the casting port timing is way off and the sleeve timing seems more appropriate. This is contrary to the info that's available on the web right now, so something seems to have changed in manufacturing, or a single run was biffed....or. They need widened to the casting, but leave the tops and bottoms alone. Deck the jug to get the piston to the top. Correct the squish band on the head if you got a head for a 47mm top end, and run a single base gasket.

I am not saying all of these jugs are like this, so it would be nice to be able to compare measurements with others if you have these jugs to compare.

Its definitely smoother running than my 47mm builds.

I will be tearing it down again, so I will degree out the ports when I do and post the info here.

 

[ImpulseRocket]

So my conclusion is, on these recent steel sleeved jugs, the casting port timing is way off and the sleeve timing seems more appropriate. This is contrary to the info that's available on the web right now, so something seems to have changed in manufacturing, or a single run was biffed....or. They need widened to the casting, but leave the tops and bottoms alone. Deck the jug to get the piston to the top. Correct the squish band on the head if you got a head for a 47mm top end, and run a single base gasket.

There are definitely inconsistencies with the sleeve port positions relative to the castings. Even with my "110" iron sleeve engine the overhangs are almost the exact opposite of the sleeve that LA Hover had with his engine. our port timing figures are completely different because of it.

 

[TheWizzerd]

There are definitely inconsistencies with the sleeve port positions relative to the castings. Even with my "110" iron sleeve engine the overhangs are almost the exact opposite of the sleeve that LA Hover had with his engine. our port timing figures are completely different because of it.

Right...

I was just basically stating that regardless of all the info out there that says you should clean these steel sleeve 49mm jugs up to match the casting, try to refrain from doing it at first. See how she runs after a minor cleanup of the slag and if it seems decent, widen the ports a bit, but do not change heights. If its a dead dog, then maybe consider matching the ports.

It is indeed a torquey little engine now. Much better low end than any of the 47mm builds I have had, even ones tuned somewhat.

Still have to work out the pipe for it to get the power band a bit higher, but I am fairly satisfied with where it is headed at this point. I could honestly leave it as it is and it would be fine...... but who the hell would do that. Only a mad man would leave it alone.

 

[TheWizzerd]

OK, tore it down again to get port timing.

Durations:
Exhaust: 159.5 ( we can call it 160 I guess)
Transfer: 128
Blowdown: 15.7

I am no porting pro....but what I have read it seems there is a discrepancy here, and these durations would give basically what its doing. Good low end, OK low-mid range, and mid-high falls flat fairly quickly.


Seems I want the BD to be significantly higher to get the power band up a bit more to the top, but I cannot do so without raising the exhaust port. I have already decked the jug for squish. Decking it more to raise the jug would get me into the top cooling fin and significantly reduce trapped volume. Would that be the way to go to spread the power band out a bit more toward the top?

Is my thinking correct here?