Need help (1965? Honda 49cc)

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Raptor05121

New Member
#1
#1
Hey guys. New member here. I'm a student @ FSU and I'm really not enjoying the mileage my F-150 gets around town. I need help getting old betsy here running. The last time I rode it, was maybe 6-7 years ago. Its been sitting in a garage ever since. No compression, and all I know about it is its a 1960's 49cc Honda with a 2-speed manual.







I was thinking about tearing it apart and seeing if I can rebuild it myself, but I found a 49cc Honda w/ a 4-speed manual online for $150. Will a four-speed increase the top speed or should I save the money and just stick with this old engine?
 
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Resto

Member
#2
#2
Your bike is a 1974 Honda QA50 K2. Your serial number should be QA50-3 followed by six additional numbers. This was the only year Honda used the Candy Orange metallic color on this bike.

It is a 49 cc OHV engine (has push rods) with a two-speed tranny (which is prone to "slip" in second gear). These engines never had much compression feel at the kick start lever even when new - and you can literally start this engine by actuating the kick start lever with your hand. If you truly have no compression as measured by a compression gauge, you will need to take apart the top end to see if you have an issue with valves not sealing properly...or a problem with piston rings. Not a very complicated engine to work on. Quite a few parts are available through your local Honda dealer, plus several online retailers + eBay. You can also find copies of the factory service manual for sale on eBay as well.

I have never mounted a Z50 (or XR or CRF) style horizontal cylinder engine into a QA50 frame - so, unfortunately, I can't give you a clear answer to that question, but....

I can envision two potential issues: 1) I am not sure if the engine mounts on the QA50 frame would accommodate the Z50-style engine. 2) The Z50-style engine may protrude too far forward and have clearance issues with the front tire - because the Z50-style engine has an OHC (with cam chain instead of push rods) - therefore the cylinder/head is quite a bit longer than the stock QA50 set-up.

This is just my guess and I may be wrong. Maybe others can give their opinions on the engine swap possibility. Let me know if you have other questions about Honda minis and I will be happy to help if I can.
 
tommie d

tommie d

New Member
#3
#3
Resto is right, it's a K2, I have one too. Mine is fender-less. The second gear slip was a problem with the K0 bikes. Honda said they fixed the problem starting with the K1 bikes but I here some still slipped, mine doesn't slip and shifts great. The engine serial # is on the left side engine case, look below the shifter. The frame serial # is also on the left side, right infront of the real axel bolt.
Stock Engine mounts will not work, but putting that engine in a QA50 frame is doable, you just have lot's of mod's to do. Someone over on Planet Mini's modified one to fit. Do a search over there and you should be able to find it.
 
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Raptor05121

New Member
#4
#4
Well I took it apart. Looks to be a stuck valve.







Anyone know how to remove it? I can't see very clearly but it looks like some kind of snap-ring?

While taking it apart, I also accidentally broke one of the piston rings too :(
 
TeamCheap

TeamCheap

New Member
#5
#5
I'd soak it in something to help loosen it up.

But to get the valve out all you have to do is compress the valve spring (just enough or you'll weaken it) and remove the two half moon shaped valve keepers that are wedged in around the valve stem.

From the looks of it it was in need of a rebuild anyway.
 
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Raptor05121

New Member
#6
#6
Thanks, I got it out and there was carbon holding it open. I just cleaned it all out and im letting the valves sit in mineral spirits. All I need now is the piston rings (ugh I wish I didnt break one, or else I could have this thing running) to come in.
 
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Raptor05121

New Member
#8
#8
Okay guys, I've got piston rings coming in, I also need new gaskets.

Question 1: The valves: how far should I tighten the first nut that holds the rocker arm? Right now I've got it a hair past to where it makes contact, but isnt pushing on the spring.

Question 2: The coil: I'm pretty sure mines dead. If I get a new one, how do I wire it up? There is a wire coming out of the stator and I'm not sure if anything inside isnt working.
 
tommie d

tommie d

New Member
#9
#9
Valve Tappet clearence is .002 for both the exhaust and intake. I can scan the wiring diagram from the owners manual if you need it.
 
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Resto

Member
#12
#12
Valve tappet clearance should be 0.05 mm (or 0.002 in.) for both valves.

Adjustment must be made with the engine cold. Remove flywheel cover and rotate the flywheel counterclockwise until the "T" mark on the flywheel lines up with the timing index mark on the crankcase flange. The adjustment must be made with the piston at TDC on the compression stroke. Both valves will be closed at that time. You can tell this because both tappets will "wiggle" if you move them with your fingers.

If the tappets are not free, it means you are at TDC on the exhaust stroke and you will need to continue to rotate the flywheel counterclockwise until the "T" comes to the timing mark again.

I would make sure that the points are OK before I would proceed to the coil. Breaker point gap should be 0.3 - 0.4 mm (or 0.012 - 0.016 in.) If the gap is OK, check to be sure the points are clean. Use a business card to drag between the points. This will remove dirt and grease if present. If the points are pitted, can try to smooth them with emery paper. New points are readily available for around $10 or so - either from a Honda dealer or on eBay. Usually easier to just replace them to begin with !

You can check the primary and secondary windings of your coil for continuity, but good results from a static test do not always mean that the coil is good. Bad coils frequently begin to act up when they get hot - even if they tested fine beforehand. Unfortunately, the best way to diagnose a bad coil is to replace the questionable one with a known working unit and compare results.

There is only one wire coming from the breaker points to the coil. The coil has a double plug on it. One side of the plug is for the wire coming from the breaker points...the other side is for the wire coming from the kill switch. On the QA50 K2, both of these wires and the coil plug are usually green. I think the wire was black on earlier QA50 bikes. The color is irrelevant. The thing to remember is that the coil connects to the wire coming from the engine and also to the wire coming from the kill switch. That's it !

Hope you get it running soon.
 
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Raptor05121

New Member
#13
#13
Tommie thanks for the links, I couldnt find gaskets anywhere. I just ordered a new set.

resto, how would i gain access to the points?
 
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Resto

Member
#15
#15
Points are mounted behind the flywheel. To inspect or clean them, turn flywheel and look through the cutout in the flywheel - you will be able to see the breaker points. Reach through the cutout in the flywheel with a Q-Tip sprayed with electrical contact cleaner (or rubbing alcohol if you don't have contact cleaner) to clean the points. Finish cleaning by dragging a business card or paper matchbook between the points.

To replace the points, you will need to remove the flywheel to access them. This will require the use of a flywheel puller tool.

Let me know if you have further questions !
 
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xspike77x

New Member
#16
#16
Anyone know of any aftermarket exhaust options that would work for this bike? I have one that I am working on as well, except mine is not as nice as his. The muffler is shot, and new ones are priiiiiicey!
 
tommie d

tommie d

New Member
#18
#18
xspike77x said:
Anyone know of any aftermarket exhaust options that would work for this bike? I have one that I am working on as well, except mine is not as nice as his. The muffler is shot, and new ones are priiiiiicey!
Click to expand...
It kind of hurts when you need a muffler and their $199, or $319 for a complete exhaust system. Ebay is your only option that I can think of.
 
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xspike77x

New Member
#19
#19
Well it does not need to be original to the bike, I just need a small 50cc exhaust that would fit without much modification. I thought smallbikes modded some kind of aftermarket exhaust to his z50, not sure about that though.
 
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Raptor05121

New Member
#20
#20
Resto said:
Points are mounted behind the flywheel. To inspect or clean them, turn flywheel and look through the cutout in the flywheel - you will be able to see the breaker points. Reach through the cutout in the flywheel with a Q-Tip sprayed with electrical contact cleaner (or rubbing alcohol if you don't have contact cleaner) to clean the points. Finish cleaning by dragging a business card or paper matchbook between the points.

To replace the points, you will need to remove the flywheel to access them. This will require the use of a flywheel puller tool.

Let me know if you have further questions !
Click to expand...
Well I mean do I need to remove the casing? The screws wont budge after sitting outside for 5 years and are just stripping on me. I'm not too keen on these kind of electrical systems. If I recall correctly, the killswitch never worked the last time we rode it. We always choked it to kill it, so I'm not sure what it needs or what needs to be checked (electrical-wise) to get it running.

Piston rings and gaskets should be here this weekend.

What oil should I run? I just emptied some milky-looking (no doubt water in the oil) oil from the crankcase.
 
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