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Discussion Starter · #1 ·
Hello, figured this was a better place to introduce myself because I already have a project:

1971 CB350k in "Light Ruby Red".

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The title is click bait, I have a garage in Bushwick that i store some bicycle and motorcycles at and work out of, but my apartment is near by and 2 of the 3 CBs I'm working on run so I ride them around and I do a lot of work at my apartment in the street or in the little concrete front yard thingy in front of the brownstone I live in. My garage is hot this time of year and I like hanging out with my neighbors.

The bike was in normal semi rough CB shape. So far I have rebuilt the carbs and spent like two weeks cleaning out the gas tank. I finally got it clean and started riding it around a few days ago. It idles high, around 3000rpm. It should be around 1100. Everything else runs great, pulls strong, no backfiring after I rebuilt and synched the carbs and tore out the one remaining rusted baffle on the right side. I noticed when I rebuilt the carbs that it they had two different model air mix screws and neither were the correct screws according to the manual and neither has an o ring or washer behind them like the diagrams show. Could those simple little air screws be causing my high idle?

I have half a mind to just order the bootleg mikuni carbs from eBay.
https://www.ebay.com/itm/NEW-Pair-Carburetor-For-Honda-CB350-CB350G-CB360-CB360G-CB360T-CL350-FREE-ship/253341233866?hash=item3afc5072ca:g:I3EAAOSwnTdaSzno

the problem is i don't know what model of mikuni carbs those are supposed to be, how do i go about jetting them? the listing doesn't even say what jets are in it. The bike did 22,000 miles in the middle of PA and then sat for the last 20 years I wanna do a compression test first and rule out other reasons for high idle and make sure the engine is strong before i order those carbs or spend any real amount of money on it first. So far all I had to do was buy it as-is with clean title for $700 in non running state, drive out to the middle of PA, rent a trailer for two bikes for $60 cause i picked up a cb550f from him too, then buy a battery and a few gallons of muriatic acid to clean the tank. plus a whole lotta pain and suffering both mental and physical to get that tank cleaned, I really should have taken a "before" pic of the inside of the tank because It had to be some sort of record for how rusty a tank could be, some PO had tried to clean it with TURPENTINE many years ago and then they just LEFT THE TURPENTINE IN THE TANK WHEN THEY GAVE UP!!!! I could murder whoever that SOB was, I could have been riding this thing two weeks ago. Turpentine is mostly water. This tank effectively sat with water in in for possibly two decades. I got it spotless with many washes of acid, sand slurry, distilled water rinses, and a mix of all three at some points. The tank still has a bunch of pinholes I patched with putty but I will seal the inside soon because pin holes are just going to keep forming if I don't.

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Discussion Starter · #5 ·
First thought would be a air leak in the carb seals or boots. You can't beat sorted stock carbs on a stock bike, just saying.
Mine too but I rebuilt the carbs myself and checked everything. The boots have cracks but don’t seem that messed up. If the boots were leaking the idle would go down as I slowly wiggle the carb pressing forward into the boots. I didn’t have any spray solvent to spray on the boots to see if that makes it go higher, I’ll try to find some next time I go to the garage.

Funny thing is I seem to remember having this issue on my cb550k0 when I was bringing it back to life in pretty much the same fashion 3 years ago. And the issue was the advancer was getting stuck at full advance from a mushroomed advancer cam end
 

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I guess another thing which might cause high idle is vacuum leak at your headers. If you had them off, or if they're not on tight...
 

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Discussion Starter · #7 · (Edited)
I guess another thing which might cause high idle is vacuum leak at your headers. If you had them off, or if they're not on tight...
I’m fairly certain it’s the points cam not snapping back from dirty springs or a rusty mechanism. I did some further searching and found people with the exact same problem and I went back in my logs for my 550 from three years ago and I did have that problem on the 550.

Basically if you’re idling in the 2,500 to 4,000 range and you know your carbs are set and you don’t have any big leaks it’s probsbly your advancer not snapping back, possibly stuck at full advance.
 

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Discussion Starter · #8 ·
Well my spark advancer was very rusty and very much not advancing, but it was stuck all the way closed, not all the way open. I cleaned it all up and now it's snapping back properly, but I can't check to see if it's advancing properly until i get my timing light on it.

I also noticed my throttle cable was frayed and twisted a little in a manner causing the cable end to partially dislodge itself from its holder where it attaches to the throttle plate assembly. I un-twisted it and carefully snipped the frayed ends and made sure everything worked properly when i put it back together.

I took my filthy air filters off and just let the carbs open and closed the choke a little.

All of this made it so my idle fell down to a normal level but under 2,000 it would sputter out and die. I drove myself nuts trying to figure out why it couldn't idle under 2000. I started diagnosing the charing system but it was going up to 13.5v like it should. Side note I need to do the white to pink wire mod on the stator wires because my '71 has the headlight switch, I can turn mine all the way off.

I decided to take the carbs off and check the slow jets again because the right carb seemed much more vulnerable to revs dropping when adjusted. Sure enough right slow jet was clogged. I pulled a small guitar string through both slow jets to make sure they were clear. Slapped everything back together and to my amazement revs fell into a proper idle range easily.

but another problem started happening: I feel like it still boggs down a little and wants to die sometime when I'm stopped in neutral. Even after I get idle set what I think is pretty well when I'm stationary before I set off. I'll ride it tomorrow and see how it goes.

Also how do I properly insulate the point cover? It has some coating on the inside but I don't think that is enough, I'm going to cut a big gasket out of a used fat mountain biking tube and see if that helps.
 

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Discussion Starter · #9 ·
I rode it around today with no headlight on, seemed like it was idling OK at just under 1500 rpm, any lower and it would want to die sometimes. That could totally be because of bad timing though I still haven't timed the bike because the tappet covers are really stuck on there and I'm going to have to break them free with an air ratchet. If all goes to plan today I'll get the leak down test done and get the bike timed and at that point I'll know what parts i need to order and then the real fun begins.

My question is do I go with metal pulley wheels on the stock tensioner or do I spend the $$$ on the KA slipper and go full bore? Doing the top end seems like a waste without doing the KA slipper but at that point it adds $160 (I could only find them in stock on eBay for $160 is that right?) to the top end job and thats not including a new chain or the boring/pistons if I want to go all the way.

There are too many upgrades available for this bike:grin: and they are all cheap enough to heavily consider but juuuust expensive enough to make you debate it in your head over if it's worth it on a $700 Honda from 1971. The slipper seems a little more important than the other performance upgrades since I'm doing a lot of stop and go riding and lots of hard pulls from stoplights. I guess it all depends on whether or not I really want to keep this bike or not. My plan is still to keep it though unless someone wants to give me $3,500 after it's done. I've seen beat up ones go for 2k around here just because they ran and my friend sold one with mismatched parts that "barely ran" for $2500 last year so who knows, some yuppie might offer me dumb money for it.

Another thing is I found a hole on the underside of the left muffler :cry:. It's small enough to tape closed and I'll see if I can weld a patch on but it sucks cause the mufflers were in good shape otherwise. I might be able to snag a used left muffler of eBay for relatively cheap. If not I might have to order new cocktail shakers with removable baffles.
 

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Yep, it's really like owning a boat... the investment to do everything right has ballooned over the last decade or so of increased popularity of these bikes and the diminishing level of available parts at now-inflated prices due to the knowledge of what's available and how much the market - us - will pay. You put a lot more into these things than ever now to do the job properly for the long haul, so the investment value is really up to the individual and whether or not they plan to keep it to get their money's worth. I'm now at about quadruple what mine is worth, but I've done a lot of things that I specifically wanted and that wouldn't matter much to a prospective buyer - which is why mine will likely be with me to the end.
 

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Discussion Starter · #11 ·
I have more pictures.

I did the white to yellow alternator bypass in the headlight bucket. The alternator puts out from all coils now at all times regardless of whether the headlight is switched on or not. Yes I know I have to get the modern rectifier/regulator combo if I'm going to keep doing this. I've been riding it around a little and it seems to have a mind of it's own when idling. About half the time I'll pull up to the stop light and it will idle correctly a little under 1500, Sometimes I'll pull up to a stop light and it'll shoot up to 2000rpm, sometimes it will drop down to <900 and want to die. In either case sometimes when I rev the throttle a little it will correct itself. I installed inline paper filters in the fuel lines and took out the screen in the petcock. I checked and flow seemed good just straight down into a cup but I have now idea how well its flowing into the carbs. How picky are the 3D carbs for fuel flow and float level? I'm pretty certain I got the floats right.

I still haven't timed the bike I'm hoping to do that tomorrow. I'm hoping a good tappet adjustment and proper timing plus new O rings everywhere will make the bike idle properly. I'm afraid to order anything or invest anything really into the bike until I can make it idle properly stock. Also still haven't done the leak-down test hopefully tomorrow too. If the leak down test shows good signs I'll go ahead and do the top end with ka slipper and new cam chain and I know at least one of my valve seals are leaking so I will fix that and I'll check everything else.

Also my speedo drive seal is shot I guess and oil is leaking all down my right side.

I love that little storage triangle so much.

I put two cut off valves on the tube under the tank so i can more easily remove it when I do the tappets and eventually the top end.

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Discussion Starter · #13 ·
Ok now my question is who the hell sells a h4 headlight lens that fits in my bucket?!? Common Motor is sold out of theirs and I don't see myself paying $110 total for a lens and LED bulb from them when the lens and bulb for my cb550 cost $28 total. Someone has to sell a h4 lens that fits in this trim. I would just use a hole saw and convert this lens but it works fine so i don't want to mess it up. I might order a used stock sealed beam lens and convert it.
 

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Ooohwee! She's pretty!

I'm of probably, absolutely no help but I wanted to say hi because - Brooklyn!! I haven't been in Bushwick since I was fifteen, spent a lot of summers there and loved every minute. I'm still homesick for NYC despite not being from there - it's the only place my heart has ever felt truly happy.

Anyhow, color me jealous for your running bike and Brooklyn zip code :p

Cheers!!
 

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Discussion Starter · #15 ·
I did tappets, the inlets were too tight, I found that out when I went to adjust the cam chain tensioner and couldn't get all 4 rockers to move. I also gapped and timed the points and made sure they were making proper contact and getting 12.5 volts. did a compression test and it measured 155 on the left and 165 on the right but I noticed carbon build up inside that cylinder when I took the headers off, I also noticed both were missing the copper gasket. The bike idles evenly and revs strongly but it still seems to have a mind of its own, now it will idle as low as 800 making me think one cylinder isn't firing right i need to try running it one cylinder at a time.
 

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Discussion Starter · #16 ·
I got my LED replacements for the gauges. The neutral one is kinda bright so I put a piece of white plastic bag over it before I pushed it into the tach. And that made it less bright.

the idle still goes all over the place when I stop, sometimes wants to die when its below 1100. I'm pretty sure it's ignition related because When I touch the right spark plug boot I sometimes feel a mild shock with the ignition timing and sometimes i don't and when I don't is when it seems like it idles properly. I need to check every step of the ignition system.

Anyway here are some pictures. Buy my 550.

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Discussion Starter · #17 · (Edited)
I think i finally figured out why it idles weird. One of the slow jets has a incorrectly drilled hole. It is defective. These are presumably the stock ones that came in the bike because it is a name brand Keyster jet. Did someone put 23,000 miles on this bike with it never actually able to idle correctly?

What is defective is that the hole is not as big as the hole in the other slow jet and it was drilled crooked, not really down the center. When I stick a guitar string through the jet that is not defective I can feel a certain amount of resistance against it and space aroend it. When I stick the same guitar string in the defective jet it has more resistance and I can wiggle it around less. I blasted compressed air through both and when you look through the jet against a light the hole in the defective one is clearly not as big as the other one and the hole is not centered. I would expect this sort of thing from an off brand jet but not name brand Keihin. Oh well. I won't know if that's the reason for idling issues until a new jet comes. The slow jets don't have a lot of clearance to begin with, they get clogged easily just the way they are, but factor in my defective one and the fact that I haven't sealed my tank yet and the defectively small hole gets clogged. When I pulled it out today and discovered this it was clogged.
 

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Discussion Starter · #18 ·
Just placed my 4into1 order. Got everything for the top end rebuild. Also bought chrome euro bars and Pamco ignition. I plan on getting a street cam for it and Mikunis down the line. I'm probably going to keep the bike like I said before. My Kream came in so I'll be doing that soon to the 350 tank.
 

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Discussion Starter · #20 ·
Ok back on this project. I got it running and rode it around for two years and had a blast. It's pretty beat up with its 25,000 miles but it still was pretty decent in the city.

I installed the pamco ignition and got it running pretty good but it always leaked oil pretty badly out of the front of number 2 cylinder between the cylinders and the cam box. So finally I forced my brother to help me pull the engine out so I could diagnose it. This is what I found:

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I'll post a pic of the inside of the cylinders later but they didn't seem damaged. They weren't visually flawless there were some what seemed like very minor scratches but they felt smooth to the touch. I have digital calipers I will measure everything tonight.

Now keep in mind I bought this bike sight unseen on ebay for $600 with a clean title and 24,000 miles from a father/son duo out in rural PA who had bit off more than they could chew and hadn't even attempted to rebuild the carbs yet and it hadn't been on the road since I think the 80s. I've put a few hundred miles on it just tooling around north BK. I think i had the carbs tuned pretty good this isn't the first vintage bike who's carbs I've rebuilt. I'm using the stock filters although they are very dirty i cleaned them as best i could.

Also the cam was badly pitted on one lobe and on rocker face, ill post a pic later. THANK GOD my buddy gave me a whole box of old cb/cl350 parts since he's built two before me. I know he fully rebuilt and blueprinted at least one cl350 engine. He gave me spare cl350 transmission too. Anyway in that box was a NEARLY BRAND NEW cb350 cam shaft and rockers. Saved me hundreds on this project.

Also one reason I am rebuilding the top end is because the bike would die at stop lights after it got hot/overheated. Like it was getting choked out or something. When dissembling I noticed the outer front stud on the number 2 side with the leak was not very tight, all others were properly tight but not that one. the leak could have just been a loose stud nut. number 2 piston head and chamber were wet with oil. Oil spraying all over the no. 2 chamber after overheating could have been killing the engine. I have to check to see if its got any leaky/bent valves. I just got my valve clamp today so ill check tonight.

I ordered an engine stand, deciding if i want to split it and rebuild the lower end/trans too. How should I test how well my valves seal? off the top of my head i know it had good compression when i got it going two years ago i don't remember the exact numbers though. I know I'm a dummy for dissembling it without checking compression again.

depending on valves and cylinder condition I may order over sized pistons and have machine shop do the valves and cylinders, I obviously need at least one piston, the problem is I can't find any cheap +3.00mm overbore pistons anywhere for sale. The rest of the bike aint in the best of shape so it's not worth the Wisecos. I was lucky and got a set of +3.00 overbore pistons for my cb550 project for like $120 off ebay a few years ago, I can't find the cb350 equivalent. I will probably have my cb550 cylinders done at the same time.

PS if anyone knows of a good machine shop in the nyc tristate area let me know:)

geoluv, where are you based? I have a studio of the Jefferson L where I'm working on my 350.
I'm based in bed stuy. Are you still working on your bike?
 
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