49mm Steel Sleeve --- She Rips!!

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TheWizzerd

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The issues seen in this first post have been resolved.!!!

Hello!! First time poster, long time lurker. I am not new to 2 strokes, and I have had several china girls that I have always been able to get running great and strong. However this 49mm steel sleeve engine is giving me some troubles.

Firstly.....sorry for the long post....

I got this engine based on the info I had been reading from @Karl Snarl @DieselTech @Street Ryderz and a few others.

I got the engine from Exgizmo on Amazon as it was the only one I could verify was a steel sleeve 49mm that I could get next day. The CDH "PK80" was another whole day out..... (yes, I know, but I needed my tinker fix immediately). It turned out to be a potentially nice engine... good castings, sleeve properly bored axially and not off center, etc... Same head as the cast CDH head I use on another engine. 1000% the same. Same squish band for 47mm even.....

This was to be a replacement for the 47mm engine I have been running for a while. The 47mm engine has been an excellent performer after porting, cylinder decking, reed, 372xp diaphragm carb, modified kx65 clone tuned as best as I could for the engine. It has incredible amount of low end able to launch from dead stop with no pedaling, great acceleration and winds out to about 52mph on a 36t sprocket on 26" wheels and climb decent hills all day long......yada yada.... Its a bull of an engine.

So, I got the 49mm steel sleeve engine, cleaned up the ports and matched them to the cylinder casting, matched the case transfers/gaskets to the jug base, raised the jug using 2 gaskets, decked the cylinder down to top of piston edge. Corrected squish band on the head (these heads are machined for 47mm squish). I windowed the piston as I usually do with dual windows. G2 with carbon reeds. I used my exhaust from the 47mm build (not ideally tuned for it, but another is in the works for the 49mm)...... yada...yada.

Done everything as I normally would on other engines and the suggestions I have read here about the 49mm steel sleeve specifically. Initially used the 372xp saw carb.

Its a dog. Has practically zero power. It runs, and runs smooth as butter, but wont get out of its own way and will not rev for nothing under load. Tried all the tuning I could as it was.....carb adjustment, ignition timing etc. and got practically zero change with any adjustments etc.

So, thinking maybe I biffed the porting.....I bought the jug and piston set from CDH to try again. This time I only cleaned up the slag from the ports on the sleeve just to see, no decking..... ran it without a reed and solid piston. Initially with a Bofeng carb, and same exhaust. Kept it as stock as I could at this point.

(fyi...the jug from CDH was MUCH worse than the Exgizmo jug. Far more slag and port overhang. Exgizmo needed little effort to match.)

No change....still a dead dog.

So I changed the CDI, magneto stator and rotor....no go... same dead dog. Put a stinger only, open kx65 clone on (the one intended for modification for this engine) thinking maybe my silencer is too restrictive for this engine....no go.... still a dead dog. Swapped in the windowed piston and reed setup with the saw carb.... no go, still a dead dog.

All this time doing the obvious things like plug swaps (just to eliminate the plugs), carb tuning (jets, needle height, whatnot), etc. reed swaps, leak checks, everything.

I have done a leak down test and everything is good there. I am unsure what the leakdown times should be at what pressures, but the case and jug are holding as you would expect and similarly to what my 47mm engines have done.

I left the simple stuff to the end thinking after all that it may be a simple fuel delivery issue. But alas, it isnt. Fuel delivery fine.

Among other things you would typically try.

I am a machinist and all the machine work (porting, decking, head work etc. are done with care with proper tooling made (for decking/head work etc.) and done on a lathe and/or mill)... but the second iteration had none of that as a baseline test.

I cannot for the life of me get any power out of this engine. The only parts that remained constant is the bottom end (cases, crank, con-rod etc.. I get practically zero change. Very low power, will not rev with a load. The fully matched ports of the first jug vs the just "cleaned up" ports of the CDH jug perform identically for all intents and purposes. The first fully matched jug runs a tad smoother.. Thats all thats noticeable.

One thing I will say about it that is has going for it at this point is its darn smooth. Smoothest running CG I have ever had, even after lots of crank balancing...but, maybe thats an indicator what may be wrong. Maybe it shouldnt be that smooth.

One thing about this engine is at BDC, the piston covers about 30% of the exhaust port on both jugs. Is it like that on al these steel sleeve jugs? Thats definitely not ideal, but I cant see how anything other than incorrect port position causing that, as the crank stroke works out fine otherwise, and 2 jugs from 2 sources being identical in that regard seems like its intentional. Could I have been unlucky and got 2 jugs from 2 sources that have really low exh. ports? Was there a recent batch that are all like this perhaps?

If any of you have any ideas what I may be missing, the help would be very much appreciated. Thanks in advance!
 

Chainlube

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I was thinking one base gasket until you said this:

One thing about this engine is at BDC, the piston covers about 30% of the exhaust port on both jugs. Is it like that on al these steel sleeve jugs? Thats definitely not ideal, but I cant see how anything other than incorrect port position causing that, as the crank stroke works out fine otherwise, and 2 jugs from 2 sources being identical in that regard seems like its intentional. Could I have been unlucky and got 2 jugs from 2 sources that have really low exh. ports? Was there a recent batch that are all like this perhaps?

That sounds like a low hole piston, try one with a high hole.
 

mony0_3

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I was thinking one base gasket until you said this:

One thing about this engine is at BDC, the piston covers about 30% of the exhaust port on both jugs. Is it like that on al these steel sleeve jugs? Thats definitely not ideal, but I cant see how anything other than incorrect port position causing that, as the crank stroke works out fine otherwise, and 2 jugs from 2 sources being identical in that regard seems like its intentional. Could I have been unlucky and got 2 jugs from 2 sources that have really low exh. ports? Was there a recent batch that are all like this perhaps?

That sounds like a low hole piston, try one with a high hole.
Have many 49mm steel sleeve engines and haven't seen a low hole piston. Even the cylinder kits come with high hole pistons. Had a couple cylinder kits where the piston didn't come within 5mm of top of cylinder. Those never made much power and I trashed them instead of trying to deck them.
 

Greg58

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If the piston is reaching TDC it is correct, if your engine is like mine it will convert back to a stock 47mm top end, I would try a bone stock 47mm on it and see what it does.
 

TheWizzerd

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Yes, they are high hole pistons. Even with high hole pistons they only came to about 2.5mm from jug top on both jugs. I did deck the first one. Performs the same as the non decked one.

I agree slapping a 47mm top end on would fix the issue, but where is the fun in that. At this point its a tinkerers imperative to get these jugs working.

Those who have these jugs, and have ported them, do you know what your top of port from deck height is, or have the timings handy?
 

Greg58

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I don't, I removed all sleeve material that was visibly overlapping the aluminum. I think I got my exhaust a little too high because mine doesn't have the bottom end I think it should, it's great after about 25 mph. I added a expansion chamber with a silencer with a small stinger that helps bottom end some.
 

Greg58

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I didn't degree mine, I wish I had. I have recorded three other engines I have, if I get a chance to remove that engine I'll get the specs then. I've got a 38mm stroke high pin engine that I balanced the crank in I'm wanting to test so I may change soon.
 

ImpulseRocket89

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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.
 

Chainlube

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

ImpulseRocket89

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