OLD CT
Well-Known Member
.002 inches or 0.05mm works.
New to Honda Z50... Engine dead. Help!
- Thread starter QRSamuel
- Start date
I just did a partial clean with Brakleen in the plug hole. I figured that wouldn't kill anything but it didn't end up helping anything either.
Don't worry about blame the only person to blame when shit goes wrong with my bike is me, and I'm grateful for the advice you are all taking your time to give me.
I will reassemble the centrifuge on the clutch again, the clutch actuating arm is not springing out properly anymore, I probably put that metal pin in the bearing the wrong way around or something. No biggy, I wanted it back together fast so I just eyeballed it, I'll visit the manual this time. It was working fine before I touched it.
This is a Honda Dax (ST50) 4 speed manual engine swapped Honda Z50. I re-torqued the head bolts and it now starts right up but still smokes. The head bolts must have snuck their way loose.
Will another solvent work in the place of gasoline? I don't have much (even any) lying around. I do have a valve compressor so I'm good to go there.
I was a bit upset when it originally stopped working, but I'm long over that now, even if it's not running correctly right now, at least it's running and that makes me happy. Just some more testing, wallet burning, and labor to go.
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This is a tough call as I'm not there .
I suppose you could get a small funnel and a bottle of isopropyl ( ?SP ?) alcohol from the drug store and fill the cylinder completely up with the piston as the lowest point of it's travel then lay a rag over the open spark plug hole and kick it vigorously until droplets stop coming out....
If I did tat I'd also drain and discard the oil because of possible dilution .
I don't know what a DAX ST50 is, if it's an auto clutch don't panic just yet, there's a dead simple clutch test once it's off the engine and in your hand .
I suppose you could get a small funnel and a bottle of isopropyl ( ?SP ?) alcohol from the drug store and fill the cylinder completely up with the piston as the lowest point of it's travel then lay a rag over the open spark plug hole and kick it vigorously until droplets stop coming out....
If I did tat I'd also drain and discard the oil because of possible dilution .
I don't know what a DAX ST50 is, if it's an auto clutch don't panic just yet, there's a dead simple clutch test once it's off the engine and in your hand .
Too late, I already disassembled it haha. I've got pictures, everything looks okay to me other than the intake valve which looks wet, but I can't see any oil on the valve stem through the intake port. I tested both with Brakleen, nothing came through either of them. There is some carbon buildup on the gasket surface of the cylinder, but that's probably from me running it while those cylinder head nuts were on the loose side. There is also some very light scratching on the side of the piston and cylinder, but I have no idea if this is normal or not.
A Dax ST50 is like a 50cc CT70H I think. It's a manual clutch unfortunately, but I'm not too worried about it.
Could you please take a look at the photos and tell me if anything is wrong? This exceeds my experience with engines, unless it's that intake valve, in which case I'll have to figure out how to fix it. Should there be any buildup on the side of the piston if oil is getting past the rings, or is it something you can't see because the engine has been run for so little time, or for some other reason? If I can get confirmation it's the rings, I'll go ahead and order a set of nippon piston rings meant for this piston, and a ball hone just in case. I'll probably use the hone again too for something else.
A Dax ST50 is like a 50cc CT70H I think. It's a manual clutch unfortunately, but I'm not too worried about it.
Could you please take a look at the photos and tell me if anything is wrong? This exceeds my experience with engines, unless it's that intake valve, in which case I'll have to figure out how to fix it. Should there be any buildup on the side of the piston if oil is getting past the rings, or is it something you can't see because the engine has been run for so little time, or for some other reason? If I can get confirmation it's the rings, I'll go ahead and order a set of nippon piston rings meant for this piston, and a ball hone just in case. I'll probably use the hone again too for something else.
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Hm ;
The carbon doesn't look bad to me, I'm guessing you used the choke to start it, after a few moments you should be able to hold the throttle at 2,000 RPM or so and open the choke fully .
The piston looks fine, I'm a little concerned about the longitudinal lines in the cylinder, remember when running the ball hone, it needs to be wet and moving RAPIDLY in and out, in and out as the drill motor runs as fast as it'll go .
After you hone it is the critical cleaning of the cylinder bore, clean it fully as well as you can then wipe with new paper towels, often a tiny bit of gray stuff will appear on the clean white towel, this is a good thing, repeat cleaning the bore with new white paper towels and Windex, remember : you want the bore, piston and rings all DESERT DRY when you re assemble it .
Good deal on the valves ! often you'll get a little dampness seepage, nothing means they're tip top and don't need further attention .
I ass-U-me you added the O-Ring to the intake valve stem ? .
The carbon doesn't look bad to me, I'm guessing you used the choke to start it, after a few moments you should be able to hold the throttle at 2,000 RPM or so and open the choke fully .
The piston looks fine, I'm a little concerned about the longitudinal lines in the cylinder, remember when running the ball hone, it needs to be wet and moving RAPIDLY in and out, in and out as the drill motor runs as fast as it'll go .
After you hone it is the critical cleaning of the cylinder bore, clean it fully as well as you can then wipe with new paper towels, often a tiny bit of gray stuff will appear on the clean white towel, this is a good thing, repeat cleaning the bore with new white paper towels and Windex, remember : you want the bore, piston and rings all DESERT DRY when you re assemble it .
Good deal on the valves ! often you'll get a little dampness seepage, nothing means they're tip top and don't need further attention .
I ass-U-me you added the O-Ring to the intake valve stem ? .
I haven't ever started it with the choke, in fact when I got this bike it absolutely refused to start with the choke and I haven't used it since. I think the carbon is from the oil burning, as it fouls the plug quickly. I don't think it's running rich but I'll go through the carb tomorrow. Since it did have that funny big bore kit on it perhaps it's running larger jets. Even if it was running rich, it is 100% burning oil, as some of it as it was dripping from the exhaust port while I was running the bike.
I replaced the o ring/seal on the exhaust side only. I am pretty sure these older style heads only have a seal on the exhaust side, I have examined parts diagrams to confirm this. But I will pull the intake valve too just in case and have a look-see.
I replaced the o ring/seal on the exhaust side only. I am pretty sure these older style heads only have a seal on the exhaust side, I have examined parts diagrams to confirm this. But I will pull the intake valve too just in case and have a look-see.
dirtbkr188
Well-Known Member
Just an FYI for you, when you have the 3-piece oil wipe rings there is a very good chance of accidently overlapping the corrugated ring ends, resulting in an oil burning situation. It usually can happen when installing the two other flat rings in place on both sides of the corrugated one.
Okay ;
You're right some years don't have the intake valve O-ing .
Best look at the # stamped into the main jet plus check the float level .
In general when you hold the carby with the float hanging down the float valve should *just* close as the float reaches parallel with the carby body .
You're right some years don't have the intake valve O-ing .
Best look at the # stamped into the main jet plus check the float level .
In general when you hold the carby with the float hanging down the float valve should *just* close as the float reaches parallel with the carby body .
TenderTendon
New Member
Just a couple observations.... The rings are definitely wrong for that piston, The oil ring is MUCH too small for that oil groove, and is doing nothing. There is WAY too much space between the rail and the spacer. I can't tell from any of those pics, but I also suspect the end gap on the top 2 rings is too large. You definitely want to check this. Cheap Harbor Freight feeler gauges are only a couple dollars and will do the job. My recommendation is to get the correct rings (or a new piston w/matching rings), de-glaze the cylinder with a 320-400 grit ball hone, check ring end gaps (with your new Harbor Freight feeler gauges). Aim for end gaps of .008"- .010". A little more or less is OK. If the gap is too small, you need to file some material off of the end of the ring. If the gap is too large. the ring is too small for the bore. Lightly coat the piston and rings with a thin oil and assemble. There's a lot of differing opinions on how to break in an engine, but the most important thing to keep in mind is this: These are air cooled engines, so accelerating the break in period is not a good idea. A lot of excess heat is generated during the ring sealing phase, as there is a ton of friction between the new rings and the freshly crosshatched cylinder wall. On an air cooled engine, that excess heat has no where to go and rings can overheat and lose tension. This is also why it's important to oil the rings before assembly. It's not so much for lubrication. It's to provide a better thermal path between the piston and rings, so the aluminum piston can pull more heat away from the rings. It's best to run the motor through a few heat cycles under light loads, while varying RPM's. It's important to have air moving across the head/cylinder during this time. If you can't ride the bike during break in, have a high CFM fan blowing on the motor. After that, re-torque your cylinder head, change the oil and give her hell...
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@dirtbkr188 I made sure the oil ring wasn't overlapping on initial assembly, however as @TenderTendon states the rings are incorrect for this piston. I wasn't sure why I was having issues as the fitment looked okay to me, but I am a novice. I'll know for next time - gaps in between the pieces of a three piece oil ring = bad. They are 12v rings and I used them as I had no other option at the time/didn't want to wait for lengthy shipping to my country. I will go ahead and order the correct rings, which have a single piece oil ring. They are inexpensive anyway so what's the harm. I'll get a hone too, unfortunately no one sells ball hones locally, only rigid ones, but it should arrive around the same time as the rings. Edit: The local auto parts shop will have feelers too so I'll grab some of those.