This is from the FSM and will give you an idea of the oil flow paths
-
Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.
AD
My CB350K4 and its problems
- Thread starter bladen
- Start date
bladen
Member
Observed increase clearance on the left cylinder exhaust valve. Set to spec and now valve chatter has reduced greatly - however this valve is quite a bit louder than the others when cold even with the correct adjustments made. So, likely have some light rocker damage but when the bike is warmed it sounds quite nice, a little excess chatter under load for that valve but it still runs strong.
I have finished with my repairs related to the oil loss incident. This included a full retune up - valves, timing and points gap, two oil changes and we cleaned the oil filter as well. The bike is running pretty good again, and feels really good to ride. It will be a while before I consider a top end rebuild to totally fix the damages, and will keep an eye on the valves as they continue to wear with regular riding.
I am very grateful to you, ancientdad, for guiding me and this community - you’ve been a huge help, thanks.
Here’s a video of the current state of valve chatter when warm:
Glad it's running well, and the excess wear on the rocker arms will make valve adjustments more difficult to set correctly but as long as the noise is not offensive then you're about as well off as one could expect under the risky circumstances that occurred.
Adjusted the cam chain as well?
You're very welcome, it's what we do here and it's what makes VHT different than so many other forums. Glad the results of the incident were repairable.
bladen
Member
So I guess I am not the most gentle person in the world. In the process of hooking up a new battery that stands taller than the previous one I pulled the ground wire a bit too hard and ripped off the tip of it. Now I cannot get it to make good enough contact with the terminal to behave. There is enough contact for excellent electric start performance but above 6k rpm it feels shuddery and the acceleration is weak and certainly not smooth.
Hard to tell from the picture where the cable connects to the battery. Is the bolt on the top of the terminal or on the front facing the tank? Could you drill a new hole in what left and connect to the battery with maybe a spacer between the battery terminal and the cable lug.
stl360+450
Veteran Member
Maybe time to replace the cable, either by buying or making one.
bladen
Member
Here’s what I did, it is working much better now. Squished the contact with washers to increase contact area. Temporary fix, I think I’ll either modify the current or replace it.
In the event that I replace it, the other side of the ground is grounded through a bolt that goes through the engine. I suspect that bolt is hard to take out, anyone have advice on how I’d go about replacing the whole wire?
Thanks for your advice!
That bolt is not hard to take out. And it should just be on the “nut” end of the upper engine mount.
If it’s not, just cut the old one off and put the new one on the “nut” end. Some 6ga wire and a M6 lug for the battery end and I think it’s M12? Ring terminal on the frame end (double check that one).
Should be able to get all the stuff you’d need at OReilly or Napa.
bladen
Member
The bike has been running great lately, but there’s been an underlying issue since I got it; the engine bogs at 7k rpm and then picks up again and accelerates strongly to redline. I am convinced it’s a fuel issue. I’ve cleaned them thoroughly, but the last time I was cleaning I discovered the right side carb has a #68 jet while the left side was sporting a #70. I figured this was my issue, so I’ve replaced it with a NOS Keihn #68 jet but bog at 7k is still there, though the bike feels more confident in general accelerating since replacing the jet.
Any ideas what my issue could be? I figure it must be an issue with the main jets as it’s so late in the power band - but now that I think of it I am starting to suspect a previous owner botched a rebuild and the jets are all sorts of messed up. It would explain why my bike needs to have the pilot screw all the way in to idle at 1100 rpm if the pilot jet is the incorrect size. I think the next step is replacing all the jets with a rebuild kit - could someone point me in the best direction for a high quality one?
Any other ideas about this issue? it’s been present through timing changes, valve adjustment, everything. Running stock airboxes and exhaust.
Any ideas what my issue could be? I figure it must be an issue with the main jets as it’s so late in the power band - but now that I think of it I am starting to suspect a previous owner botched a rebuild and the jets are all sorts of messed up. It would explain why my bike needs to have the pilot screw all the way in to idle at 1100 rpm if the pilot jet is the incorrect size. I think the next step is replacing all the jets with a rebuild kit - could someone point me in the best direction for a high quality one?
Any other ideas about this issue? it’s been present through timing changes, valve adjustment, everything. Running stock airboxes and exhaust.
bladen
Member
I’ve ordered the deluxe rebuild kit from 4into1, my intention is to replace only aftermarket brass and keep what is original. Will update with results!
bladen
Member
Filters are new and OEM! Appear to still be quite clean after 1500 miles. I’m thinking fuel because the bike picks up again after the bog at 7k and pulls very smoothly up to 9.5k, sounds to me like a troubled jet. I will test it without filters briefly to see if anything changes, but I’d expect it to run quite lean. Thanks for your input!
bladen
Member
Carburetors semi-rebuilt per visual inspection of wear and tear and originality to the 722A carbs.
replaced float seat
replaced main jets with #105 from the #86 that where in them.
replaced pilot screw on left carb
replaced float on right carb
calibrated float levels
She runs better than ever, again. No longer stumbling at 7k and much healthier feeling through the revs. However the idle has been very hard to tune and the carbs still idle highest with the pilot screws all the way in, even an eighth turn from seated and the bikes revs just drop. I will rebuild them again with more consistency and see if it improves and post a video of how the bikes idle is behaving.
bladen
Member
Chasing the issue of right side carburetor requiring pilot screw to be seated to run. This symptom to me means pilot circuit is too rich at idle. Upon investigation of replaced brass, the left side carburetor has 4into1 brass and the right side has whatever came in it, unsure if its original but it does not have the Keihin stamps. The left side secondary emulsion tube has an air passage in a different spot than the new brass, I wonder if this is causing my issues.
Note the far right emulsion tubes top hole is in a slightly different location. This has to matter right, or are the passages large enough in the carb body to compensate?
Note the far right emulsion tubes top hole is in a slightly different location. This has to matter right, or are the passages large enough in the carb body to compensate?
bladen
Member
Looks like have a whole other issue to solve now. Almost went down today, glad my training kicked in and I kept it steady.
True. However the hole placement and sizing is a critical factor.
Well that sucks. Time for a new tube and a patch on the inside of the tire to help keep the spot from chafing the new tube.
bladen
Member
Thinking I’ll just replace everything that doesn’t have the Keihin stamps and see how it feels. So far the replacement parts have done nothing but help. I’m going to also make sure all the air bleeds are clear but I swear I have been thorough with my cleaning haha!
Trust but verify.
bladen
Member
Here is a video of the pilot screw behavior (acting like an on and off switch for a high idle when bottomed out). Besides this, it’s running quite well on factory specs and has a smooth idle. I believe the culprit of my issues was a worn needle jet on the right carb, the tip was worn and angled.
oh and the tube and rim strips were replaced.
oh and the tube and rim strips were replaced.
bladen
Member
Upon further riding, I am frustrated. The bike now has issues above 6k rpm, it feels rough, sluggish, and like it’s running out gas (I have a full tank). I’m lost though because I just rebuilt the carbs again this morning but the only change I made was to the needle seat, needle jet, #35 idle jet, and I cleaned everything thoroughly. The bike idles decently but at stops the rpm’s drop to 800 and it almost dies without a little bit of throttle.
bladen
Member
these 722a carburetors are becoming my enemy… here they are broken down on the bench, secondary emulsions tubes didn’t have the slot in the top so i’m gonna assume that is what was causing my high rpm bog, as for my rich idle? i’m tempted to set the floats to 25mm to see if that helps, they are set at 26mm currently.
Last edited by a moderator:
stl360+450
Veteran Member
Lowering the float height to 25mm would make the idle richer, since that would raise the fuel level in the bowl.
The left carb mixture screw seemed to be acting strangely in the video of post #71 — sounded rich to me. I assume this was not happening on the right? The left carb has replacement brass. I would focus on acquiring original brass for the left side and trying to put everything in the carbs to factory settings. Then, go from there.
Sometimes you can find parts lots on eBay, like this one. I did not check the contents of this listing carefully. I have also purchased used carbs and rebuilt those or swapped parts between different carbs.
The left carb mixture screw seemed to be acting strangely in the video of post #71 — sounded rich to me. I assume this was not happening on the right? The left carb has replacement brass. I would focus on acquiring original brass for the left side and trying to put everything in the carbs to factory settings. Then, go from there.
Sometimes you can find parts lots on eBay, like this one. I did not check the contents of this listing carefully. I have also purchased used carbs and rebuilt those or swapped parts between different carbs.
bladen
Member
Alright well this last rebuild was my last it seems. I got off work and decided to rebuild the carburetors after seeing the ebay listing (thanks) showing main jet emulsion tubes with the little hole a tiny bit lower than the ones I put into my carburetor and figured that cannot be right.
First, I checked spark plugs. Left was dark and sooty, right was white and chalky. Yeah, it was feeling awful so no surprises there.
So, I replaced both main jet emulsion tubes with the ones that came on the bike, set both floats to 26.5mm, and cleaned the pilot screw circuit a little more. I was very careful in installing its oring and washer. I also cleaned a small airway that vents into the world I assume for excess air pressure in the float bowl.
Something here fixed it. No more high end problems, idles at factory spec. 3/4 of a turn out from bottom on both sides and I get a nice even idle. Not perfect, but with some fine tuning I bet it will be. And all it took was 5 consecutive rebuilds!
Glad you finally got it sorted. Now don't let it sit and gum up the carbs again, and you'll be golden!
bladen
Member
The rain came and I was not able to ride for some time, but yesterday the sun was back. The ride I went on was more spirited than the one I took when testing and I’ve found some issues again. Bike runs very lean and hot at high rpm. I lowered the floats to address but it enrichened the idle and the top end is still very lean. Lean enough to not want to accelerate past 8k, if I open the throttle it hits a power plateau at 7k and might backfire at 8k and does not want to accelerate any further. Upon inspection of plugs:
At idle, slightly rich:
At mid to high rpm, very lean:
Additionally it feels that in full throttle around 5k - 6k it will miss a power stroke and stumble briefly. Rough acceleration all around, especially at operating temps.
I’m running stock airboxes and the jets are stock sizes but non oem, I have oem replacements on the way.
Rich at idle, lean at high rpm feels like I should up the main jets to 110s which I have on hand and then raise the float to 26mm again. If this does not fix it, I will check timing and the advance mechanism. I just recently did the cam chain adjustment, valves, and timing and felt that the bike sounded a lot better under load in low-mid rpms.
I’m getting frustrated chasing my tail with this stuff, but I guess it’s all a part of it. I wonder what the underlying issues truly are..
At idle, slightly rich:
At mid to high rpm, very lean:
Additionally it feels that in full throttle around 5k - 6k it will miss a power stroke and stumble briefly. Rough acceleration all around, especially at operating temps.
I’m running stock airboxes and the jets are stock sizes but non oem, I have oem replacements on the way.
Rich at idle, lean at high rpm feels like I should up the main jets to 110s which I have on hand and then raise the float to 26mm again. If this does not fix it, I will check timing and the advance mechanism. I just recently did the cam chain adjustment, valves, and timing and felt that the bike sounded a lot better under load in low-mid rpms.
I’m getting frustrated chasing my tail with this stuff, but I guess it’s all a part of it. I wonder what the underlying issues truly are..
stl360+450
Veteran Member
Seems like a good plan.
I’d do one change at a time.
Jets first, test run, then float if needed.
Assuming of course that advance function is working properly, timing is set properly and anything spark-related has been eliminated.
Jets first, test run, then float if needed.
Assuming of course that advance function is working properly, timing is set properly and anything spark-related has been eliminated.
bladen
Member
I am finding conflicting information, can someone tell me exactly what the primary carb jet size is on the 722A carburetors? I have a NOS 68 and a kit 68 in, but it’s running lean in the midrange to high rpm, wondering if it’d prefer 70s.
edit: Nevermind, I found the pinned thread. Will keep the 68s.
edit: Nevermind, I found the pinned thread. Will keep the 68s.
bladen
Member
Alright! Carbs rebuilt with some more OEM parts: emulsifier tubes, idle jet, float seat, pilot screw. I also put in the 105 big jet and set the float to 26mm, used heavy duty gear oil to seal leaky throttle felt seals. kind of starting from square one. Idle was immediately smooth, which was nice. However I noticed the right header got warm much faster than the left.
Took her for a test ride. Bike still hits a wall at just above 7k and does not want to accelerate further, feels like it drops a cylinder. Left plug is white after sustained rpms, right looks tan.
Right:
Left:
Next I think I’ll rebuild the petcock and re check the timing to see if that fixes it. If it’s not fuel, it must be spark.. right?
Took her for a test ride. Bike still hits a wall at just above 7k and does not want to accelerate further, feels like it drops a cylinder. Left plug is white after sustained rpms, right looks tan.
Right:
Left:
Next I think I’ll rebuild the petcock and re check the timing to see if that fixes it. If it’s not fuel, it must be spark.. right?
stl360+450
Veteran Member
It's definitely worth considering the ignition components. Sometimes a coil will fail under heavy load, yet work under normal load. This can also stem from issues with the charging system not keeping up under heavy load.
Can you remind us about your ignition coils? Type? Age?
Can you remind us about your ignition coils? Type? Age?
bladen
Member
Coils were either replaced by the previous owner or are original to the bike. I’ll swap them left for right and see if the condition swaps cylinders.
You might not have to physically swap them, just swap plug wires and yellow and blue wires from the points.
stl360+450
Veteran Member
Are they the blue or possibly off-white Tek coils?
bladen
Member
View attachment IMG_5216.jpeg
Here’s an older picture of the condenser / coils
Looks like it’s about as old as my dad.
That is original, condensers too. And BTW, I'm a dad and I'm older than those coils.
stl360+450
Veteran Member
And it's Nippon Denso rather than Tek. Old doesn't mean bad and new doesn't mean good, but it's probably worth trying the swapped leads to explore the coil function further.
New coils and condensers are a decent insurance policy, although if the condensers check out on a multimeter I wouldn't necessarily replace them. I've used the black reproduction coils from 4-into-1 that are similar in construction to the OEM units.
bladen
Member
Okay I’d like to try this, so the yellow and blue wires coming from the points swap into the yellow and blue wires coming from the coils.
Like this:
And put the left spark plug boot on the right cylinder spark plug and vice versa?
Like this:
View attachment IMG_6102.jpeg
Thanks!
stl360+450
Veteran Member
That looks right. Now see if the high tension wires can reach to the opposite plugs.
Yep, as long as both plug wires can reach the opposite sides then you're set to test it that way.
bladen
Member
Thank you all for your help. After riding I found that the left cylinder is still lean, and the right cylinder is also pretty lean still. I will ride it more and see if it takes some time to show up. I then put 110 main jets into the carb today, feels like it got a little more power but it still is producing white plugs on the left and nearly white plugs on the right.
All things considered it is running quite nicely, the idle is especially smooth after getting the oem 35 jets. The mid range and high end feel like they may be missing a few horses but it accelerates smoothly all the way to 9k. I will continue working on adjusting things and slowly figuring it out.
Next up I think I’ll get a good petcock cleaning in, replace the points and the rest of the ignition system (the points i noticed today are due).
All things considered it is running quite nicely, the idle is especially smooth after getting the oem 35 jets. The mid range and high end feel like they may be missing a few horses but it accelerates smoothly all the way to 9k. I will continue working on adjusting things and slowly figuring it out.
Next up I think I’ll get a good petcock cleaning in, replace the points and the rest of the ignition system (the points i noticed today are due).