1976 XL350K2 - An Off and On Project

ancientdad said:
Yeah, I'd check the cable routing and lube it a bit before suspecting the carb. Those are big heavy slides, with the added spring pressure from the original Mikuni slide return spring it's hard to believe it would be sticking.
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I was a little surprised by this behavior also. At first I thought the cable had tightened up due to colder temperatures in the morning this fall, but adjusting the cable didn't solve the issue and then I noticed that I could get the slide to drop fully by flicking the throttle, most of the time. Hopefully the cable is to blame.
 
I would polish up the harder slide surface with scotch brite etc. and check for any burrs or dents at edges, as Jensen said the body is very soft alloy. I've seen very light corrosion on slides cause intermittent issues.
 
ballbearian said:
I would polish up the harder slide surface with scotch brite etc. and check for any burrs or dents at edges, as Jensen said the body is very soft alloy. I've seen very light corrosion on slides cause intermittent issues.
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The slide is actually pristine. I purchased two VM32's for my CB450 around 2011 or 2012, but eventually returned to the Keihin carbs. Then, around 2016, I bought this XL350 and eventually replaced its stock carb with one of the VM32's. Later still, I replaced the slide with a brand new one to increase the cutaway. There is no corrosion on the slide.

I will have a look at the groove in the slide for anything out of the ordinary.
 
I've been fiddling around with things on this bike trying to nail down the hanging idle issue. The slide and throttle cable seem to be operating very smoothly and I cannot locate any air leak around the carb insulator. This led me to suspect the mixture.

The biggest change over the last several months involved replacing the previous carb boot, which had split in two last spring. There were two other changes that I introduced at the same time. The first involved installing a gasket between the boot and the head, which I had neglected to do previously. The second involved lowering the needle clip one slot to the lowest position (raising the needle).

This morning I had a sudden thought that I might have installed the needle in such a way that it was not held in place by the slide spring, so I decided to remove the slide and have a look. It was installed correctly, but this allowed me to confirm the needle position that I wasn't totally sure about before. I decided to return the needle to the second lowest clip position, thereby lowering the needle one step. When I started the bike it was a little jumpy, but felt like it had more power. After warming it up, I adjusted the air screw for a strong idle and did a few laps up and down the street and around the block. So far, the idle has not hung up. The air screw is at about 1.5 turns.

The plan now is to ride it to work tomorrow and see if the problem has been solved.
 
I have not had many opportunities to ride the XL350 since making the adjustments noted in the previous post, but the hanging throttle issue did recur on the couple of rides I was able to do. I am wondering if the throttle cable might be frayed inside the sheathing and I am considering making a custom throttle cable whenever I get the chance. If anyone has recommendations for a DIY throttle cable kit, I am all ears. I have seen some on eBay, but have not made a purchase.

I have owned this bike for almost ten years and I have been perplexed off and on by a relatively simple task: adjustment of the brake pedal height. I was in the garage last week and decided I would get down to the bottom of this issue and came away thinking that there is no way to adjust the brake pedal height on this motorcycle. It appears that the design of the XL350K2 has the brake pedal arm making contact with the foot peg in its stationary position — the brake pedal free play is adjusted in the usual way via the rear brake adjusting nut.

The bike did not come with the Owner's manual and the reprinted shop manual only addresses adjustment of the rear brake for the XL350K0, which does permit separate pedal height and free play adjustments. I have since gathered Owner's manuals for both the K0 and K2 models, along with a used parts manual for the K2. I'll include the relevant bits below to document the major change in the design of the rear brake pedal/linkage and the corresponding adjustment procedures from the Owner's manuals.

XL350 K0:

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XL350 K2:

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I just acquired the XL350K0 owner's manual in the last week. It was interesting to me for a couple of reasons.
  • There was a Montana registration slip folded up in the manual from 1976. A Google search suggests that this former owner is now 77 and still associated with the address on the slip.
  • Various pages in the manual have small rectangles of text pasted over whatever the original content was. I assume this was done to correct errors in the original printing. This is my only K0 owner's manual, so I'm wondering if this is common with the early model manuals or, perhaps, common in general. Examples:
    • A small bit over the spark plug gap specification.
    • A section pasted over a step in the air cleaner maintenance procedure.
    • Half a page is pasted over in the oil change procedure.
 
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I've been using a MOTOMASTER throttle cable kit from Amazon and it's great. The kit has enough material for multiple cables and I've made 3 so far with plenty left over. You'll need a good soldering gun to get enough heat in the cable/ferrule joint to endure the solder makes a good connection. Kit is $17.99 and well worth it.
 
ericfreeman said:
I've been using a throttle cable kit from Amazon and it's great. The kit has enough material for multiple cables and I've made 3 so far with plenty left over. You'll need a good soldering gun to get enough heat in the cable/ferrule joint to endure the solder makes a good connection. Kit is about $19 and well worth it.
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Thanks for the suggestion. Was it something like this one? I suppose a micro torch could be used, too, if my soldering iron is too weak?

Edit: I see that the brand matches what you mentioned. I'll prolly take the plunge on that one then. Thanks!
 
When the brake pedal arm is in the full up position and in contact with the foot peg is the pad even with the foot peg as it shows in the picture in the owners manual or does it sit lower than that?

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RobMan said:
When the brake pedal arm is in the full up position and in contact with the foot peg is the pad even with the foot peg as it shows in the picture in the owners manual or does it sit lower than that?
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I'll share pictures, one from 2016 right after I got the bike and another from 2022. I noticed that the point of contact on the brake pedal arm has a small notch now (not visible in the photos) and I am also contemplating ways to dampen that contact point. Note that the picture you annotated, Rob, is from the K0 manual and that side cover has also been changed for the K2.

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Has the foot peg or bracket that it attaches to the frame been bent down any by chance? It doesn't look like it from the photos but just wondering as that would affect how high the brake arm could go. How much higher do you want the pad to sit? The only thing I can think of is to modify the pad by welding a 1/4 inch shim of metal on top of the pad or modifying the arm itself so the pad sits higher which would involve cut and weld.
 
RobMan said:
Has the foot peg or bracket that it attaches to the frame been bent down any by chance? It doesn't look like it from the photos but just wondering as that would affect how high the brake arm could go. How much higher do you want the pad to sit? The only thing I can think of is to modify the pad by welding a 1/4 inch shim of metal on top of the pad or modifying the arm itself so the pad sits higher which would involve cut and weld.
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It doesn't seem like anything is bent, but I can't be 100% sure. I was really surprised to find that pedal height adjustment was eliminated.

The reason this would bug me off and on is that I would feel/hear the contact between the pedal arm and the peg and think I should lower the pedal height to get a small bit of clearance to avoid that clinking sound, not to mention the wear that has notched the arm slightly over time. The position of the pedal is comfortable, but it felt wrong to have that metal on metal contact in the stationary position.

The linkage from the drum to the lever is a cable and another idea would be to replace that cable with a brake rod — I think that might allow me to control the pedal height by adjusting by the spline position of the pedal arm (parts #9 and #10 for the K2).
 
If it's the clanking against the foot peg that bothers you, I would get some large heat shrink tubing, cut several one inch pieces and stack them over the brake pedal under the foot peg area one at a time and apply some heat to keep them there.
 
I did not understand it was primarily the noise of the arm hitting the peg that was the problem. I thought it was the pad was sitting too low and affecting braking. Maybe take an inch or two of fuel line slit down its length and glue it on the arm at the contact point with Gorilla glue. It should hold for a while and would come off if it caused issues.
 
boddy said:
I would get some large heat shrink tubing, cut several one inch pieces and stack them over the brake pedal under the foot peg area one at a time and apply some heat to keep them there.
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I've been searching for damping materials that might slip over the arm, but hadn't considered heat shrink tubing. That's a good thought.

RobMan said:
Maybe take an inch or two of fuel line slit down its length and glue it on the arm at the contact point with Gorilla glue
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Yeah, that could do it also. Since the brake arm has a rectangular cross section, is possible that a trim piece could even sit on the top edge, with a little help from an adhesive. I have something left over from my CB350 seat pan, probably too narrow, but something similar could be good.
 
I braved the frigid outside temperatures (8° F or -13 °C) to visit my detached garage yesterday with the goal of removing the throttle cable and carburetor to investigate the sticking throttle issue. One of my thumbs was completely numb by the end of those twenty minutes despite wearing my thin leather riding gloves while I worked.

The cable worked well for a at least a few years after I swapped the OEM carb for a Mikuni VM32. In order to make things fit, I wound up using a cable from Niche Cycle Supply (Throttle Cable w/ Elbow Mikuni 45"). It's difficult to simulate the performance of the cable off the bike, but one thing I notice is that when simulating the closing of the throttle by pushing the cable from the throttle side, the elbow separates as shown below. Then, when the two sections of that elbow come back together, it seems that one piece can catch on the other without fully seating. If one repeats the procedure, sometimes it catches and sometimes it seats fully — this reflects my experience that short blips of the throttle would often get it to close, but sometimes it would take 2 or 3 blips.

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The spring on top of the carburetor slide should be strong enough to prevent this from happening, but maybe not if the cable is pinched somewhere else by the gas tank. I do not see any signs of damage to the braided steel wire, so this is the only possible explanation that I've come up with for the frequent throttle hanging that I was experiencing.

All of this makes me want to build a better throttle cable and I am slowly gathering all of the required pieces. I already have the Motomaster cable kit from Amazon. It has the cable ends, sheath, wire, and barrels, but I separately ordered a 90° cable end adjuster for the throttle side that threads into the throttle housing just like the OEM cables. I also ordered some stainless steel flux to make sure I get a strong bond on the barrels.
 
Time in the garage has been scarce this winter. Sometime around the Super Bowl (a month ago) I managed to build a homemade throttle cable using the Motomaster kit I had purchased on Amazon. I was planning to use a standard vertical cable adjuster on top of the Mikuni VM32 along with a 90º threaded cable adjuster compatible with the XL350 throttle housing.
  • The first cable I produced did not have enough free play. I managed to install it, but there wasn't enough slack for the slide to reach the bottom of the bore, so I had to cut it and start over. Strike one.
  • I made a second cable with sufficient free play and then discovered that there was not enough space between the carb top and the frame/tank for the cable to make a smooth bend. Strike two.
  • I salvaged the second cable by removing the small end on the carb side and installing a 45º elbow that threads into the Mikuni carb top. I got the cable made, but didn't have time to install it right way.
I finally got the cable installed yesterday and initially the cable felt tight. I was worried that it still lacked sufficient space to bend at the top of the carb, but decided to lube the cable to see if it would make any difference. The lube made a huge difference, so I moved on with the installation, including a new two-stage UNI air filter.

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Another issue I had run into with the bike was related to the rear brake pedal. I determined that there is no pedal height adjustment for the later XL350s and that the pedal rests against the underside of the footpeg by design. This creates a bothersome metal-to-metal contact every time the brake pedal is depressed and released. I purchased a length of u-channel rubber of an appropriate width (10 mm) and cut a small piece for the top side of the pedal arm, using a modest amount of Loctite Stik'n Seal glue to secure it. This seems a decent solution thus far.

I managed to get a test ride in this afternoon. The throttle cable has a little too much slack, but works smoothly and is not sticking, which was the impetus for building a cable in the first place. I will ride it like this for a little while and then either shorten the cable slightly or build another one.

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I have some plans to freshen up this bike over the summer. This includes a high compression piston kit and a cylinder that is ready to go with it. I also have a smaller rear sprocket to shift things more towards street riding.

After seeing @RobMan's success pulling dents on his CB450 tank, I would also like to try the same on the dents I inherited from the PO. This will also give me the chance to alter the paint scheme that I chose previously, which was a large departure from the factory style. I really like the 1978 XL350 tank decal and I'm thinking of doing something similar in colors that I prefer. In fact, I just ordered a used tank so I can take measurements because, unfortunately, I know of no decal set for that model. I played a little with Google Gemini today to mock up one possibility.

Original 1978 XL350 Tank:
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Mock-up in green, silver, and white:
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The stripes would ideally continue across the side covers as on the 1978 model. The wing decal that I purchased is a bit smaller than shown, but is all white.
 
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I forgot to add pictures of the cable ends for the homemade throttle cable to my post yesterday.
  • The inner cable was cut to approximate length and passed through all of the necessary components.
  • The line was passed through the cable end, frayed slightly, and then soldered in place. I used stainless steel flux and standard electrical solder. I used both a micro torch and a standard soldering iron — both worked well enough.
  • The final inner cable length adjustment was made on the other end before it was passed through the corresponding end, frayed, and soldered.
  • I used a rotary tool to clean up any inner wire that protruded from the finished solder joint. This is especially important on the throttle side since the barrel must be able to fit into the throttle tube and rotate more or less freely.
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I received the cheapest 1978 XL350 tank on eBay today. I plan to use this to measure the graphics for my summer tank painting project.

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It's the same tank pictured above — I used a picture from the listing to do the mock up.
 
I put about 25 miles on the new throttle setup this afternoon. It was ideal weather for a ride and I was out in the south suburbs where one can expect to string a few green lights together on a good day, cruising along at 45 mph — a nice cruising speed for this bike.
 
It is bring your dirt bike to work day today. I think I'm the only one, but I guess I didn't widely announce this unofficial special occasion.

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Right at the end of my long ride last weekend as I left the bike to idle while I opened my garage, it died. The neutral light wasn't lit, but it fired right up. I suspected a loose battery connection and, sure enough, when I checked it this morning the ground lead had slipped loose. I'm using a tiny 6V agm battery with spade connectors, but I ordered an agm that should be the same size as OEM and will eventually install that with proper bolt mounted connectors.
 
I am continuing to gather parts for a planned refresh of this bike over the summer. In order to fit the current exhaust, I hastily removed the passenger peg mounts from the swingarm to avoid interference between the muffler and the swingarm. I have been looking at used swingarms on eBay and at some point it occurred to me that CMSNL might have one. They actually have five new ones, priced at $400, but then I noticed there was a listing for an imperfect part for about $75. The discount stems from a couple of scratches that get through the paint, but I decided that was something I could deal with based on that discount level, so I ordered that swingarm along with new bushings tonight.

A year or two ago I had noticed a CB360 camshaft (14101-369-000) on sale for $277.73 and bought it for my strategic reserve. Right now there seems to be only one camshaft available on CMSNL for the CB360G and it carries a price tag of $904.28. I am thinking it pays to watch prices and availability.
 
stl360+450 said:
I recently received the imperfect swingarm from CMSNL and I am pretty happy with the purchase. The imperfections are minor and well worth the more than 75% discount.

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The end of the semester and start of my summer are approaching quickly, too, and I am looking forward to working on this bike.
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Yes, always very nice to score cheap NOS parts this way. I bought a complete front fork leg of a 1961 CB72, for less then 50 euro, because it was scratched.
 
Yesterday I received a flange and boot for Mikuni carbs from Mikuni Oz in Australia. The flange is slotted for 62-75mm spacings, which is very convenient when fitting a VM32 on a variety of heads. I had modified a commercially available intake boot previously and may swap it out with this over the summer. Cheers to @cb350 for making me aware of this!

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jensen said:
Yes, always very nice to score cheap NOS parts this way. I bought a complete front fork leg of a 1961 CB72, for less then 50 euro, because it was scratched.
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For sure. I think I need to make this type of shopping a regular practice! (It's a secret.)
 
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stl360+450 said:
Yesterday I received a flange and boot for Mikuni carbs from Mikuni Oz in Australia. The flange is slotted for 62-75mm spacings, which is very convenient when fitting a VM32 on a variety of heads. I had modified a commercially available intake boot previously and may swap it out with this over the summer. Cheers to @cb350 for making me aware of this!

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For sure. I think I need to make this type of shopping a regular practice!
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Psst, don't tell anyone, it's a secret....
 
ancientdad said:
If I hadn't already spent so much time on my stock 450 boots for the drag bike engine, I would buy a pair of those.
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As soon as I saw them on @cb350's CB350, I knew I wanted to try one. They advertise it for the VM34 and a few other carbs, but it seemed to fit nicely on my spare VM32 this morning.
 
stl360+450 said:
Yesterday I received a flange and boot for Mikuni carbs from Mikuni Oz in Australia. The flange is slotted for 62-75mm spacings, which is very convenient when fitting a VM32 on a variety of heads. I had modified a commercially available intake boot previously and may swap it out with this over the summer. Cheers to @cb350 for making me aware of this!
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Great to see! Glad I could help.
 
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