The "mystery muffler" referred to in the previous post belongs to this bike. A past client, Jeff C. from Oklahoma, has a fun collection of Gen-2 & -3 white VFRs, three of which were full-on projects of mine at some point. This one is his "rider," and it's a 1986 VFR700F2. When coming out of winter storage earlier this year, the bike presented itself with a no-start condition. Jeff focused on the carburetors as the culprit, but he also verified that the fuel pump was supplying the magic juice and replaced the plugs. We were texting back & forth but neither of us thought to do a basic spark check…which eventually showed itself as the root cause; more on that later.
Not knowing much of the history of this bike, Jeff decided to have the carbs redone and tuned, volunteering to deliver the bike to me on his way to other duties in this area. I only had a few days with the bike so I got right to work on the carbs, which proved to foreshadow several maintenance surprises.
(Below) While removing the carbs, I found three of the eight boot clamps had been replaced with loose-fitting hardware store hose clamps. The boots were old but three of them were reusable while the fourth was physically damaged beyond use. Next I found that the metal airbox plenum base had been ground out around the brass tubes which protrude from the carb tops. I've seen this before, and it's a result of trying to install the plenum on the carb set which was prematurely secured by the underside screws/brackets. The carbs need to move apart slightly to install over the brass tubes…then everything gets snugged up. By hogging out those radius' you create a permanent unfiltered air leak at each carb. Fortunately, I had a spare plenum on hand.
Next, I found a bent enriching plunger — not the end of the world, and would actually continue to function as long as the now-weakened soft brass didn't break off. This I've also seen before, and again, it's a result of trying to force the plunger on or off the carb without first removing its linkage. We also sourced its replacement. Various jets and passages were clogged and several of the carbs' screw heads were damaged by use of an improper screwdriver, so they were replaced with new.
While the carbs were off, I did a quick valve clearance check…all OK.
Not knowing much of the history of this bike, Jeff decided to have the carbs redone and tuned, volunteering to deliver the bike to me on his way to other duties in this area. I only had a few days with the bike so I got right to work on the carbs, which proved to foreshadow several maintenance surprises.
(Below) While removing the carbs, I found three of the eight boot clamps had been replaced with loose-fitting hardware store hose clamps. The boots were old but three of them were reusable while the fourth was physically damaged beyond use. Next I found that the metal airbox plenum base had been ground out around the brass tubes which protrude from the carb tops. I've seen this before, and it's a result of trying to install the plenum on the carb set which was prematurely secured by the underside screws/brackets. The carbs need to move apart slightly to install over the brass tubes…then everything gets snugged up. By hogging out those radius' you create a permanent unfiltered air leak at each carb. Fortunately, I had a spare plenum on hand.
Next, I found a bent enriching plunger — not the end of the world, and would actually continue to function as long as the now-weakened soft brass didn't break off. This I've also seen before, and again, it's a result of trying to force the plunger on or off the carb without first removing its linkage. We also sourced its replacement. Various jets and passages were clogged and several of the carbs' screw heads were damaged by use of an improper screwdriver, so they were replaced with new.
While the carbs were off, I did a quick valve clearance check…all OK.
(Right) Later, I would find that these carbs' sync settings were waaay off. By the time I got to this point, I was not surprised by the lack of proper tuning.
In the end, it was a good decision to address these carburetors.
In the end, it was a good decision to address these carburetors.
With the rebuilt carbs remounted, I quickly encountered the original no-start situation. There was absolutely no indication of this engine wanting to light off, so the first thing I did was to remove #1 spark plug and check for spark. Nothing. Well…there's yer problem.
Even on these relatively simple bikes, a no-spark issue can be the result of a number of failure points; a check of the service manual lists ten possibilities in the trouble-shooting section. But what I needed to focus on were only the items which could cause all four plugs to fail. That quickly eliminated things like pulse generator(s), coil(s) or plug lead(s), as these would require multiple items to fail at once, highly unlikely.
I began at the beginning, as it were, with the ignition switch, which has a simple continuity test in the manual: OK. Next was the kill switch, likewise a continuity test: OK. Next on the list was the Cam Pulse Generator, again, a simple continuity test: FAIL. The Cam Pulse Generator is a Hall-style (magnetic pick-up) sensor located on the front cylinder head and sensing a trigger on the front intake cam gear. This is wired directly to the Spark Unit (black box), offering lots of potential information to the Spark Unit. If this information is missing, there's no way the black box knows when or even if to signal the coils to fire the plugs — no spark.
The next hurdle was to find a replacement. Honda no longer supplies the part, but I did locate one at CMSNL.com in the Netherlands. Before committing to that, however, I reached out to internet friend Bazza, and asked if he could lend us the part to check my diagnosis. He could and he did, and a week later we had a running engine. Baz was even kind enough to sell us the part. Another example of the VFR community coming together.
Even on these relatively simple bikes, a no-spark issue can be the result of a number of failure points; a check of the service manual lists ten possibilities in the trouble-shooting section. But what I needed to focus on were only the items which could cause all four plugs to fail. That quickly eliminated things like pulse generator(s), coil(s) or plug lead(s), as these would require multiple items to fail at once, highly unlikely.
I began at the beginning, as it were, with the ignition switch, which has a simple continuity test in the manual: OK. Next was the kill switch, likewise a continuity test: OK. Next on the list was the Cam Pulse Generator, again, a simple continuity test: FAIL. The Cam Pulse Generator is a Hall-style (magnetic pick-up) sensor located on the front cylinder head and sensing a trigger on the front intake cam gear. This is wired directly to the Spark Unit (black box), offering lots of potential information to the Spark Unit. If this information is missing, there's no way the black box knows when or even if to signal the coils to fire the plugs — no spark.
The next hurdle was to find a replacement. Honda no longer supplies the part, but I did locate one at CMSNL.com in the Netherlands. Before committing to that, however, I reached out to internet friend Bazza, and asked if he could lend us the part to check my diagnosis. He could and he did, and a week later we had a running engine. Baz was even kind enough to sell us the part. Another example of the VFR community coming together.
Ignition system for the 1986 VFR 700/750. Honda Service Manual
Because of the parts delay, Jeff was forced to leave his bike with me to get back home, which gave me some time to poke my curious nose around his bike…a good thing, as it turns out.
The first thing I noticed was that the rear brake torque arm was installed front-to-back, missing the spacer washers and wasn't safety wired with cotter keys. This all kinda still worked, but wasn't, you know, right. Looking further, I see that the rear axle was also installed backwards. In the process of righting those wrongs I realized that the rear brake caliper slider pin wasn't, ahh, sliding; rusted in place, a common issue (below). Honda can still help out with that part, so let's clean up the caliper pads and pins and set all of this right. While installing the rear wheel, I took the time to clean and adjust the drive chain. Along the way, I discovered that the rear brake lever wasn't activating the brake light, but the adjuster was stuck in place requiring removal of the footpeg assembly to allow access.
Next, I checked all the hydraulics and found this soup in the clutch reservoir (below). Okay, let's flush the front brakes and clutch (the rear brake looked fresh). I also removed the clutch and front brake lever assemblies for a clean and lube which smoothed the lever action considerably. Later, on the test ride, I still didn't like the front braking action in general, so the decision was made to replace the unknown brake pads with some upgraded EBC HH pads. Again, a fortuitous decision, as I found the left-side pad spring installed backwards (this is becoming a common theme), limiting the outer pad's movement. So, a full cleaning/lubing had the brakes back in shape.
The first thing I noticed was that the rear brake torque arm was installed front-to-back, missing the spacer washers and wasn't safety wired with cotter keys. This all kinda still worked, but wasn't, you know, right. Looking further, I see that the rear axle was also installed backwards. In the process of righting those wrongs I realized that the rear brake caliper slider pin wasn't, ahh, sliding; rusted in place, a common issue (below). Honda can still help out with that part, so let's clean up the caliper pads and pins and set all of this right. While installing the rear wheel, I took the time to clean and adjust the drive chain. Along the way, I discovered that the rear brake lever wasn't activating the brake light, but the adjuster was stuck in place requiring removal of the footpeg assembly to allow access.
Next, I checked all the hydraulics and found this soup in the clutch reservoir (below). Okay, let's flush the front brakes and clutch (the rear brake looked fresh). I also removed the clutch and front brake lever assemblies for a clean and lube which smoothed the lever action considerably. Later, on the test ride, I still didn't like the front braking action in general, so the decision was made to replace the unknown brake pads with some upgraded EBC HH pads. Again, a fortuitous decision, as I found the left-side pad spring installed backwards (this is becoming a common theme), limiting the outer pad's movement. So, a full cleaning/lubing had the brakes back in shape.
Finally, with the front end suspended, I checked the steering head bearings and found the worst steering bearing situation I've ever encountered. The bearings were reluctant to move, but the real issue was a severe "notch" in the center position. No question that we had to service the bearings, which required a hammer to loosen the bearing lock nut. I've never seen anything like this entire situation, actually. A bearing replacement/upgrade to tapered bearings had everything moving like butter. Here's a short video showing the issue.
So, even though this was a running, riding bike last Fall, when we poked around under the plastics, there was no shortage of surprises. But, as was the case here, a competent DIYer can put this bike right with a service manual, a few days of garage therapy and a couple hundred dollars.
I think that there's an overall lesson here, one which I learned early on in my time with these V4 projects. That lesson is that initial looks can be deceiving, and what lurks beneath can cost you time, money and even your safety. The previous work performed on this bike reeked of amateur-grade sloppiness. I'm an amateur and I'm the first to encourage others to learn to work on their machines. It's satisfying, saves tons of money and you know it's done right. That is, IF you at least follow some qualified guidance while learning. I've said many times here that I consider a service manual at your side to be a must-have tool. And a torque wrench would have helped immensely in this case. If you're not willing to do it right, you shouldn't be messing with something that could hurt you or someone else — brakes being a prime example.
And as always, caveat emptor.
I think that there's an overall lesson here, one which I learned early on in my time with these V4 projects. That lesson is that initial looks can be deceiving, and what lurks beneath can cost you time, money and even your safety. The previous work performed on this bike reeked of amateur-grade sloppiness. I'm an amateur and I'm the first to encourage others to learn to work on their machines. It's satisfying, saves tons of money and you know it's done right. That is, IF you at least follow some qualified guidance while learning. I've said many times here that I consider a service manual at your side to be a must-have tool. And a torque wrench would have helped immensely in this case. If you're not willing to do it right, you shouldn't be messing with something that could hurt you or someone else — brakes being a prime example.
And as always, caveat emptor.
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