Severe engine misfire fixed; Fuel line found pinched in clip

[k7mdl]

Bought a used '87 Venture couple months back with 45K miles on it, very nice condition. Worked great for almost 200 miles. On the second day, coming back home from some local shopping (and the wife's first ride on it) the engine died out on the freeway like it lost electrical or no fuel. After 10 minutes was able to start it, and it ran for 100 yards and died again. 10 more minutes goes by and it started again, was able to run with low RPM the remaining 2 miles home.

 

Felt like a "no fuel" issue, perhaps a clogged line/filter or fuel pump failure. Bike is 20 years old, found rust chips in the filter, not enough to clog the filter. Pump working fine. Maybe the line itself at the tank (running in reserve position full time as previous owner always did). Went through electrical, pickup coils OK, ignition coils OK, wires/caps/plugs OK but replaced them anyway. Engine seems to be running long term now, but backfiring through carbs, hard to keep running without choke on, running rough. Symptoms seemed to keep changing along the way.

 

Cleaned all connectors, swapped out TCI no change. In place cleaning carbs, I spray carb leaner in ports and pour down some SeaFoam, no better. Did run better when carb spray shot down throat of 2 left carbs though (#1 and #2). Feels like a fuel issue still at play - maybe reason for misfire? Can make bettrer or worse with carb adjustments. Maybe carbs need severe cleaning. Compression all about 190# - great numbers for a 20 year old bike! Replaced all diaphragms. I have one good used spare if someone needs just one. 3 others have a small pinhole or about to develop one to three pinholes so might work for a short while if some is desparate.

 

Got a Morgan Carbtune Pro and it sync'd up OK despite the constant misfire. Nice unit by the way. Sync'ed my 2007 Venture also really easy. Backfire through the carbs seemed to go away but still have misfire through exhaust. After much fiddling with carbs, including removing them for cleaning (but not tearing them open) and using some carb cleaner and light scraping to remove the heavy carbon buildup on the intake valves. No leaks that I can find in the intake manifold boots or vacuum hoses or caps. Still get misfire. Float bowl fuel level was OK. I did find in reinstalling the carbs the engine would run for a while and quit. Now I definately have a fuel problem. Pumped fuel and rust chips out of tank. The thick braided fuel line from the fuel pump passes through a spring clip at the top rear of the carbs. It squeezed the hose shut when in the clip (softened up over the years). I think early in the process I pulled the hose out of the clip I never put it all the way back in until now since it was hard to reach and that silently cured the fuel flow issue. Thinking back I suspect this is the orignal reason the bike died on the freeway. It gets just enough through to fill the bowls at idle speed or engine off. Still have misfire though.

 

Seems like cylinders 3 and 4 are the main culprits now, but #1 and #2 react the most with carb cleaner down the throat. Really stumped at this point, read practically every related post on this forum for months now, found some similar threads, lots of good tips for certain things, but none a perfect match to my issues.

 

Took it to the shop. Valves OK. Carbs tore apart, new rubber plugs and gaskets were needed, evidence of some leakage between sections, gaskets dried out, rubber plugs dried out. Now all system checked OK, new oil, coolant, lube, valve alignment. Still same problem. Constant misfire through the whole RPM range, especially under load. An intermittent in the pickup coils was a guess, but could not confirm. #3 and #4 seem to be affected.

 

This is a long post reflecting the long journey and many hours in the garage and shop chasing and diagnosing and such. Problem is getting old by this point.

 

Yesterday brought bike back home from shop. Now convinced all systems are working as designed, today I took a deeper look at the intermittant pickup coil theory. I wanted to somehow verify this before spending a load of money on this. Myself and shop ohmed them out to be in spec (about 116 ohms) except shop thought one was half value at one point. I am experienced in electronics design and repair (have tools and know how to use them ) so I put my dual trace oscilliscope on the pickup coil connector and compared them all with engine idling at 2K RPM. You get about 12 to 15 volt spikes - 1 positive pulse followed immediately by one negative pulse for each pass of the magnet. Engine still misfiring regularly, never saw a missed pulse though, and all stayed at the same voltage peaks. The pickup coils are declared good.

 

Yesterday reading through some more postings here I picked up some more good tidbits. One person mentioned that these engines run very well on 3 cyclinders and other than lack of performance and low fuel mileage, it can be hard to tell if (only) one cyclinder stops working (bad plug wire for example). This would be key advice later on.

 

I pull the #3 plug cap, misfire goes away, but runs about the same, rough. Install #3 and pull #4 and misfire is back but runs rough as before. Like the shop said, #3 and #4 do not seem to be pulling their weight. But why only #3 causing misfire? A mystery.

 

With all systems verified to be working, but the bike not working right, I figure it was time try something new. I connected #3 input to the ignition coil to the input of #4 coil, left #3 coil disconnected. Engine now runs smooth but at 1000 RPM higher. Revs up clean. This verifies pulse train from pickup coils to TCI to #3 ignition coil input verified OK even though it was the misfire cylinder. You might now suspect the #3 ignition coil, wires, cap, or plug, except they all check out with test gear. Now that it is running nice on 3 cylinders I connect input to #4 ignition coil to the #3 ignition coil. Stays running nice. The suggestion that it should run smooth on 3 good cylinders rings true enough. RPM is 2000+ at idle through all of this to keep it running before. Short test ride is great. Then sync the carbs and set proper idle and all is as it should be now. Test ride is sweet.

 

So the faults:

1. Squeezed fuel hose at clip near top rear of carbs (found very late in the process, unknowingly resolved early on)

2. In cleaning all connectors while chasing the original problem, symptoms changed to misfire and unknowingly had swapped the #3 and #4 ignition coils after testing them. Leads are not labeled and the longer connector from the wire harness actually goes to the rear ignition coil.

3. The coil input wire swap happened before the fuel line pinch was unknowingly resolved so there was never a period when the engine ran "right". Symptoms changed over time, but with the carb adjustments now thoroughly fiddled with, was hard to tell why or when.

 

The good part of the story:

1. With my work and the shop visit the bike has a documented clean bill of health through all systems (except the shocks that leak air).

2. Visiting the Yamaha shop with my wife to get parts 1 week after this all started she sees the 2007 Venture and declares it ours, and directs that I sell the other one that left her stranded on the side of the freeway. (she is a Project Manager, makes decisions fast, especially when it means the possibility of her helping push the bike along the street far from home:cool10:).

3. Given #2 above the '87 bike being out of commision all summer did not prevent us from doing about 6 one- and two-day road trips since May 28th to July 9th.

 

I now have a commute bike that seems like a lighter weight sport bike compared to the '07 Venture. There is definately more passenger space on the '07 though. I am 6'1" and find the '07 to have better leg/foot space for me and the passenger. The '87 passenger toes practically hit my calf and do often at stops manuevering into the footpeg slot behind the fairing. I like the louvers closing off the heat, and look forward to opening them during the winter commutes. Commuting is 1-up only so the passenger issues are not applicable. I added a backrest to teh '07 and the handle bars seem like a long reach still, despite my long arms, so several hours into a ride I feel it.

 

Not sure how much longer I will keep the '87, but I enjoyed working on the bike, getting to know the '07 better via the similarity to the '87, and experiencing a bike I had wanted for many years in the 1980's but could not afford back then. I rode a XS1100 then. I added a full fairing and lowers, air shocks, double buckets, luggage racks, detachable side cases, engine guards, hiway pegs, and sliding back rest. Toured New England for 3 years with the wife before kids came along and moving to Washington (Seattle area) in 1985. Had a XS750 Special in Hawaii for 3 years before that 1100. Sold the 1100 in 1991 and after 18 years of carpooling kids in a cage, I (we actually) am back into big bikes again now.

 

Great forum here, hope this post helps someone in the future.

 

Happy trails,

 

Mike

[Venturous Randy]

Wow Mike, great post and information. Sometimes these things can just about drive us crazy. Sounds like if you do decide to sell it, someone will get a good bike.

RandyA

[mbrood]

Mike,

 

What a classic... and HONEST review of your efforts.

 

You certainly aren't alone in fixing one thing only to lightly mess up two others... so you start working on one of them and something ELSE pops up and we start to think the gremlins are eating us up...

 

But to paraphrase Pogo:... "We have found the enemy and the enemy is us..."

 

My own experieces have been with a side note... it seems that if I DON'T draw blood somewhere along the line... I'll be taking it apart to fix what I messed up... forgot the locktite, an "extra" spring laying on the floor, etc.

 

Thanks for the write-up... it definitely made me grin at a few memories.

 

I FIXED my class (error #4) by carefull disassembly, carefull soldering the main connector pins, carefully put it all back and it worked flawless... and then I saw the housing "clip" that I had forgot to put back... grrrr...

 

I often invite my mother's dog to come out and "assist"... perfect excuse why I didn't "see" the clip or bolt or...

 

I used to have a beautiful male Shar Pei that was my sidekick... he was absolutely PERFECT help in the garage. He would nudge a wrench or bolt a few inches away and then quietly sit on it. By then "I" was busy looking for the stupid thing, looking high, low and inside places it couldn't POSSIBLY be hiding and all the time the dog would look at me like "You REALLY need to find something, huh?" He had just a GREAT sympathetic look. "You should keep track of your stuff..." Then he would get up to "help"... and suddenly, in the middle of the floor, out in the open lies that item... grrr...

 

But who can blame the help?

http://www.bergall.org/temp/relaxed.jpg