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Discussion Starter #1
Ok. I had the bike running pretty well for a while, it wasn't perfect but I was getting closer. Then it started fouling the right cylinder plug and causing the right side to quit running. I would pull the plug, clean it up and put it back in and all was well for a few miles. I tried adjusting the air mixture screw (after syncing the carbs as best I could) and it didn't seem to make any difference (I know the bike has to be warmed up to make carb adjustments). All the while the left cylinder has been running great, plug looks good and all.

Now a more troublesome issue. I have been trying to figure this out, mostly by trial and error, which means I get the bike running and go for a ride, bring it back and make adjustments. I pulled the carbs and cleaned them, again. Well, it starts right up on both cylinders and I can rev it fine, I pull out and it spits and sputters in first, pulls well in second and then the right cylinder dies. Turn around and limp it back on the left cylinder and when I park it and shut it off, I get real black oil coming out of the header to muffler joint in the right side exhaust! What? I did seal the header to muffler joint as was suggested here when I got the new mufflers, but obviously its not sealed anymore. So I can get it running on both cylinders again without much problem, but then I get a lot of smoke out of the right side because there's all this oil in there.

Now, I'm just assuming its oil that's in the exhaust. I had to add a little oil today but I really haven't been running it that much. I checked the compression again today, 150 psi in the right, 152 in the left. The points are spot on, both sides, as are the valves. I know the compression is right on the line for a top end job, but I'm trying to avoid that if possible.

I honestly don't know where to start. Help.

Thanks
Ben
 

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Sensei
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Ben, Regardless of the PSI reading, you are "pumping oil" out the cylinder and into the exhaust. It is possible that that same oil actually increases the PSI reading (deceptively) allowing you to believe it is better than it actually is (would be) dry, and your rings are REALLY bad........

However, fuel in the oil sump (unburnt by-pass or leaked in through bad petcock/ bad needle and seats, or bad float levels) can raise the oil level to the point this symptom can occur...... SMELL THE OIL.... IF there's ANY gas smell, don't run the engine... Find out how the fuel is getting in, and fix it , then change oil.....

Let us know.....
 

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Discussion Starter #3
66Sprint, Thanks for the reply. The bike didn't run when it came to me and who knows how long it had been since it ran. Before I got it running, I checked the compression and it was the same as it is now which leads me to believe that the condition of the rings hasn't changed. I am not throwing bad rings out the window though. How could I tell if the rings are bad? Let it sit for a while and check the compression again, then put some oil in the cylinder and check? Ideas?

As for fuel in the oil sump, the petcock is brand new and I know it doesn't leak. The float levels are to spec (.73 inch I believe, has been checked several times). As for the needle and seat, they're original and could be the problem I suppose, but I have smelled the oil on several occasions (including today) and didn't smell any gas. I'll definitely check that again though. I guess I should get carb rebuild kits?

Also, I forgot to mention in the original post that the right side spark plug is not oil fouled and actually is quite clean. I will get new plugs and check for sure though.

Appreciate the help.

Ben
 

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Sensei
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That oil is getting into the cylinders somehow...You just need to figure out how..... Bad head gasket leaking in?..... Worn valve guides?...... "Stuck" oil ring on that piston?...
Several possibilities that could still show semi-decent compression readings.....

Unfortunately, the cure for any of them is tear-down and check......Unless you can think of a different possible cause......
 

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Discussion Starter #6
Alright, I need a little more help. Many questions to follow.

I haven't had a chance to tear the top end down yet, but what should I be looking for? I'm guessing that the rings are bad for sure. If they are, what else do I need to do? If the cylinders are ok, should I still lap them out while I have it apart? Then, how do I determine what size rings I need and where can I get them?

I think I've read on here that you can check to make sure the valves are seating by pouring a little acetone on them and checking for leaks. How about the valve guides? Is there a telltale sign that they're bad?

I know I'll need a new gasket set, and I see there are several on ebay. Any brands better than the others?
Also, which carb rebuild kits are the best? I know I've heard that some are junk.

I've had the valve cover off and everything seems to be ok there. The cam journals aren't excessively worn, nor are the cam followers and the cam chain is in good shape as far as I can tell.

I realize I just asked for a lot. If anyone has any good general info on rebuilding a top end, I'd really appreciate it.

Thanks
Ben

P.S. This bike has 15,500 on the clock but I don't know anything about its history.
 

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I'm there with you, check my build thread. The ring size depends on the piston size. Piston/ring size depends on how much meat you have to take off the cylinder walls(boring) to clean up scratches and/or return the whole thing to the same dimensions from the top to the bottom of the sleeve. If there's next to no scratches and the dimensions are uniform top, middle, and bottom, a good honing may be all that's required(for the cylinders-put in new rings regardless). If that's the case, AND there is no damage to the stock piston( measurements and tolerances can be found in the manual downloadable on this site) STANDARD ring sets are needed. If the piston is damaged, STANDARD pistons and ring sets. If the cylinder needs to be bored, it can be bored one quarter of a millimeter bigger in 4 increments, up to one mm larger TOTAL, then it's time for new ones. There are piston and ring sets for each of these overbored sizes(.25, .5, .75, and 1.) A very wise man from the SOHC4.net website named Two-Tired taught me that Honda carb parts are available and worth the money so you don't have to guess whether they're good or not. Your call, though.
 

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Also, do you have the cam out? No way to tell if the journals are toast without looking under it...While you're in there you need to pull the tensioner and slipper to see if they're decaying also.
 

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360fan said:
A very wise man from the SOHC4.net website named Two-Tired taught me that Honda carb parts are available and worth the money so you don't have to guess whether they're good or not.
Hey, did he happen to name a seller or give easy I.D. names for our 360 jets?
 

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I'll see what I can find out. He's a 550-4 junkie, has like 4 of them, but if they're available, he probably has a source. which ones, the 3 tops, or the main and secondary group?
 

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Not really any point in doing a teardown and not putting a new set of rings into it. Time is money department. Given what you observe in the exhaust joint, a totally clean plug is odd - check the end of the tailpipe - is that oily or dry? My 500T has an oily header/muffler joint on the left side - that's because the shifter shaft seal leaks a little and it drips onto the pipe at exactly the strategic point. Look for oil leaks. A common reason for oil in the tailpipe but not the cylinder is a missing/disintegrated exhaust valve oil deflector.
 

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360fan,
Try and get a reference name for all of them , I mean, we know whay size they all are, but when looking on carb sites its hard to know exactly which shape are ours. If you can get an identification list for all 6 jets, posting that info in the 'Tech info/Parts Guide' page would be a great service :D
 

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Discussion Starter #13
So I finally got a little time to tear the top end down. I was pleasantly surprised at how "good" things looked. I haven't had a chance see if the valves leak, but that is a definite. Looking through the other 360 rebuild posts, I see that the cam journals are about the same or better than most. The cam chain was tight and appears to be in good shape. The tensioner and slipper look healthy with no signs of cracks or deterioration, but I still have to check the thickness of both. I haven't inspected them closely, but the cylinders seem to be in decent shape. I did see one definite scratch in the left. All I have for measuring is a micrometer so I only measured the top and bottom of both cylinders, in two directions at each. The largest difference I found from top to bottom was in the left cylinder and it was .44 mm, the bottom being larger diameter than the top. The pistons at the skirt were spot on the specs from the shop manual. The piston pin holes and piston pins were also spot on.

Questions.

All of the cylinder measurements I made were in the 66.xx mm range. The standard specs in the shop manual are in the 67.xx range. Is this a measurement error on my part? How are the cylinder I.D. on my bike smaller than the standard specs?

Is the .44 mm difference from top to bottom in the cylinder to large, or can I just hone the cylinder and put in new rings? Also, can I hone the cylinders myself or is that a farm out job?

Thanks for all the replies and help guys, it is greatly appreciated.

Ben
 

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Hmmm - I just checked the 360 manual (Honda), it doesn't seem to give a spec for cylinder taper.
That's odd, because it's listed in almost every other model manual, and is ridiculously small in most cases - like "less than 0.005 mm (0.0002)" for a 450, which is a typical value for these old Hondas.
I bored out my 450 due to excessive taper. It was about 0.001" - my machinist thought that was fine, but I couldn't deal with it.

No way are your cylinders smaller than stock, your measuring device is not up to the task.
Find someone with a good set of micrometers and take measurements. Most places will do it for free.....

Maybe someone else knows the spec for taper on a 360 ??

So not sure what to say - your decision.
 
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