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Discussion Starter #1
Hi all,

I rode my bike for the first time last night and it died on me! Luckily I didn't go far, it was a test ride. It's a 75' Honda CB360T. The previous owner did a lot of work and said it had issues with the floats, so I took it to a shop and had it gone through. This shop changed the jets and properly tuned the carbs, I did a fresh oil change with 10/40 non-synthetic. It was idling a little low so I turned up the idle a little bit, took it for about 1.5 mile ride and it ended up dying when in first gear at a stop sign. (no electric start) I kicked it over about 15 times over 15 minutes and ended up pushing it home (It's a 1-2x kick bike usually). I started it about a 45 minutes later after sitting, took a few kicks and it started up again, when I put it in gear it died, and I tried kicking it over a few times with no luck. The shop mentioned it was smoking a little bit, he said to do an oil change which I did, the smoked seemed to go away, he said if it didnt it may need a top end rebuild, but it "seems ok" anyone know what I might be able to check for? Im new to these bikes but I am also engine savvy, just new to these in particular.
 

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Discussion Starter #4
I guess I'll clean them up and ride it again and see if it happens again before buying new ones?
Im not sure what they looked like before the shop did the carb work.
 

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You getting terrible fuel consumption too? Do you have any exhaust system at all on it?

Compression test is always a good start point if somebody questions important engine bits.
8 is a cool plug 77 or 7 is hotter :/ although it looks like you are flogging the coal to it now. maybe stop the needles one notch if the carburetors have such an adjustment.
... when you said you were going to have a shop check it out I was skeptical, your results confirmed that was a waste of money, yes?
 

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You getting terrible fuel consumption too? Do you have any exhaust system at all on it?

Compression test is always a good start point if somebody questions important engine bits.
8 is a cool plug 77 or 7 is hotter :/ although it looks like you are flogging the coal to it now. maybe stop the needles one notch if the carburetors have such an adjustment.
... when you said you were going to have a shop check it out I was skeptical, your results confirmed that was a waste of money, yes?
When the shop solution is "change the oil again", it's time to look for a new shop.
Better yet, learn, and do it all yourself.

Sent from my Pixel 3 XL using Tapatalk
 

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Discussion Starter #10
You getting terrible fuel consumption too? Do you have any exhaust system at all on it?

Compression test is always a good start point if somebody questions important engine bits.
8 is a cool plug 77 or 7 is hotter :/ although it looks like you are flogging the coal to it now. maybe stop the needles one notch if the carburetors have such an adjustment.
... when you said you were going to have a shop check it out I was skeptical, your results confirmed that was a waste of money, yes?
I just got this bike, so I have no idea what the mileage is like yet. Never a waste of money when it comes to safety. I come from a classic car and vespa background so for my first "real bike" I found a shop that works on old bikes, and requested a basic run around of the bike for safety, mostly for things for myself to do and what to flag, if the bike is safe, what the previous owner did wrong, etc.
 

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If you are still dealing with vacuum operated carbs directly connected to pod filters and your exhaust system has been raped, then your motor would be operating way too lean for how it was originally designed. To combat the lean situation people create by opening up the breathing, they flog the fuel through the carburetor by changing jets and settings in an effort to make it run less lean. Yours has been made to run so rich it is producing huge volumes of unburnt carbon which is going to soot up your pistons and valves and exhaust something awful.
Safety is all fine and good but the thing has to run under it's own power or it is useless as a motorcycle. If you ask a shop to check for safety issues, they are not going to be looking for motor issues they are going to be checking steering, wheels and brakes. Previous owner messed up your motor.


add: where does your crank-case breathe from? If it can't breath when the pistons go up and down then it will be sucking or blowing oil into places it should not be.
 

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Discussion Starter #12 (Edited)
Thanks... The shop that looked at it said these carbs have original jetting, they installed new needle and seats and fixed the stuck floats. So re-jetting could help resolve the issue here? I found a pretty extensive print out in a parts box from the previous owners order from 6sigmajetkit.com I have a bag with 115-k main jets, and the parts list says 110-k main jets as well, so it's safe to say there are 110 mains in there now, this print out says if its lean to use the 115. Which direction do the numbers go to get it more lean, or better yet, what would be a good jet size to try from here.
 

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That's the whole problem, the carburetor jetting was designed to work with an air box that you no longer have and an exhaust that has been altered :| you have no base line to set things to, you are carburetor tuning in uncharted territory and your carburetor is not a simple venturi slide type carburetor. If it was I would say lower the main jet needle by one or even 2 notches on the cir-clip. You have a CV carburetor, they don't adjust anywhere near the same.

... if a shop guy can tell original jets just by looking that would be truly impressive and if the carb was unchanged it would be running lean not rich, that I can pretty much guarantee you.
 

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Thanks... The shop that looked at it said these carbs have original jetting, they installed new needle and seats and fixed the stuck floats. So re-jetting could help resolve the issue here? I found a pretty extensive print out in a parts box from the previous owners order from 6sigmajetkit.com I have a bag with 115-k main jets, and the parts list says 110-k main jets as well, so it's safe to say there are 110 mains in there now, this print out says if its lean to use the 115. Which direction do the numbers go to get it more lean, or better yet, what would be a good jet size to try from here.
Pod filters on CV carbs (vacuum slide) are problematic. The issue is that it isn’t as simple as they just run lean. They will also run rich in certain rpm and throttle positions. You won’t just luck into the correct jet configuration. Tuning CV carbs with pods is usually a game of compromise. You might get good WOT performance at the expense of throttle response, or you might be able to get good steady state performance and decent throttle response but WOT performance stumbles. Very rarely will it work across the board as well as it ran with the OEM air box. CV carbs use the pressure differential before and after the carb to operate the slides. When you remove the still air volume that the air box provides, you’ve mucked up the balance, and it is very hard to get around that.

All that being said, your plugs look extremely rich, but it depends what range that was in when they fouled out. Pilot jets and air fuel mixture screws determine the air/fuel mixture at idle and in lower rpm and throttle positions. The main jet determines a/f mixture at WOT. The needle taper and height is responsible for mid rpm and transitions between ranges and throttle changes. Your carbs may even have an accelerator pump to add to the complexity.

You will need to do plug chop runs to get the different regions dialed in as best as possible. You have to find an isolated straight road that you can do some rather high speed runs. You need to run the bike in the range you are testing for about a quarter mile and hit the kill switch and pull the clutch. Pull to the side of the road and pull the plugs and give them a read. Make adjustment and repeat. Every adjustment will require removing carbs. You can see this will get tedious, right?

My personal methodology is to get the idle running right first. In order to do this, I start with a valve adjustment and a carb sync. Then start with the pilot jet. With the right pilot jet in, the mixture screw should be between 2 to 4 turns out. If you mixture screws are on the engine side, they are fuel screws. Screwing them in leans the mixture. If the screws are on the filter side of the carb, they are air mixture screws, and screwing them in richens the mix. If the adjustment screw is required to be too far out, or too far in, you need to go up or down on the pilot jet size.

Once the idle is good, I go do my full throttle plug chops, and get the main jet right.

Then I do the needle height to get mid rpm and throttle response as good as possible. I do the needle after WOT because any change to the main jet will require adjustment to the needle height.

After all that I go back and sync the carbs.
 

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Discussion Starter #15
Pod filters on CV carbs (vacuum slide) are problematic. The issue is that it isn’t as simple as they just run lean. They will also run rich in certain rpm and throttle positions. You won’t just luck into the correct jet configuration. Tuning CV carbs with pods is usually a game of compromise. You might get good WOT performance at the expense of throttle response, or you might be able to get good steady state performance and decent throttle response but WOT performance stumbles. Very rarely will it work across the board as well as it ran with the OEM air box. CV carbs use the pressure differential before and after the carb to operate the slides. When you remove the still air volume that the air box provides, you’ve mucked up the balance, and it is very hard to get around that.
Are there other pod filters that might work better with these bars? Or is pretty much either stock air box or pod filters. My test ride was less than 2 miles, but I am not sure how fouled they were prior to the test ride. But I didn’t get passed 3rd gear. I cleaned the plugs and also buying some new ones today, going to take another test ride and check the plugs after the same ride. Maybe everything is ok and they were just filthy before huh? Doubtful :)

So, a plug chop is new to me. I’ll try this today, sounds easy enough for testing. After pulling over and checking the plugs you say make an adjustment, you mean back at home with jetting or some kind of adjustment on the fly after pulling over? It actually idles really nicely.

Thanks for all the tips Im glad boards like this are around. My uncle owned a Harley shop for years but he lives 6 hours from me, too bad for me!

Even buying Mikuni carbs would require some tuning but are they a good investment and better style carb? Debating on where to invest my time and money to get things right.
 

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you didn't ride it enough to get a fair assessment reading the plugs, ride more and observe for other symptoms.
If you buy used ones from a place like I was at today, carburetor swap would be a great investment. Have you ever been to a motorcycle wreckers yard :I is awe inspiring.
 

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Discussion Starter #17
you didn't ride it enough to get a fair assessment reading the plugs, ride more and observe for other symptoms.
If you buy used ones from a place like I was at today, carburetor swap would be a great investment. Have you ever been to a motorcycle wreckers yard :I is awe inspiring.
For sure. I only got a 1.5 mile ride before it died on me. The plugs may have been pre-fouled already. I put new plugs in and the left side threads were less than perfect so I am waiting for a thread tap to clean up the threads. Will report back with test ride results! Hope to be dialed in... somewhat soon :) Appreciate all the help so far.
 

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If it was running and then it wasn't, that would lead me to think it could be a fuel delivery problem.

Check for clogs, dirty filters, kinked hoses, stuck floats, bad petcock...etc.
 

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Have you checked the electrical system? Run diagnostics on that? Usually when I have a died and won't restart problem when warm it's because the coils or the ignition trigger is failing. I am assuming your bike runs points so it's unlikely that they are the problem, but might want to check a few things in the electrical system, esp those janky ass honda fail prone coils.
 
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