1978 Bonneville T-140V

[Frank]

Rocky, I'm jealous that you are so close to British Cycle Supply. Thank goodness they are only a phone call away though. I'm not jealous of your winters though. I left NH 21 years ago and have not missed winter yet.

Seeker, thanks for the tip on Northern Eagle. From what you both have told me my problem with the tail lamp is not common. I will continue working on it.


Now I have a new problem.

I was riding home from work the other day and about 2 miles into the 8 mile ride, I was approaching a red light, throttle closed. The engine quit. I tried to restart but no dice. I pulled to the side of the road and tried some more. I got it started but it ran terribly. Just chugged, couldn't rev it up at all. So I called my wife to bring me spark plugs. She did, I changed them, no spark. I found the fuse on the negative battery cable had blown. I sent my lovely wife to get new fuses. (Before she got back a fellow biker stopped at the red light, asked me if I was out of gas. I said no, I needed a 20amp glass fuse. He went home and found 30 amp fuses and got back to me before my wife did.) I put the fuse in and with some difficulty it started. Yes, I called my wife before I took off on her, leaving her to wonder if I had been abducted by aliens or something. So I continued my journey home but I was lacking a considerable amount of power. I had enough to keep me out of trouble in traffic but if I tried to open her up it bogged down.

Before this happened I had not been having any trouble except the tail light thing.

I'm going to look at my Boyer and make sure it has not somehow come loose affecting the timing. Then I will just poke around and scratch my head some and come back and look here for help.

 

[gumpt1oo]

Not sure but it sounds like you could have a charging problem. Check to see what condition your battery is in, I know from experience that if the battery drops lower than about 9v mine runs terrible, if you can get it to start in the first place!

 

[Frank]

Well, I'm embarrassed. The loss of power was due to the air valve being completely closed. When I was broken down on the side of the road I was trying everything to get it to start. I don't usually need to choke it but I tried it out of desperation and accidently left it choked all the way home and when I parked it in the garage.

But before I discovered the choke being on, I did check the battery and with no load it had over 12 volts. On my ride home when it was running poorly I had tried shutting off the lights to see if it got better as I had read somewhere that if it was a low voltage situation that little bit would help. If the poor running is due to choking the air supply then the extra juice doesn't seem to help one bit. Imagine that.

But I still don't know what caused the fuse to blow in the first place. Is 20 amps sufficient? I used 20 because that's what was in the fuse holder that disintegrated shortly after I got the bike. I seem to recall reading somewhere that it might supposed to be more like 30 amps.

 

[Frank]

When all else fails read the instructions. I just looked at the original owner's manual for 1977 Bonneville (I'm more and more convinced that I have a 77 that wasn't titled until 78) and it says "Fuse rating (Amperes).......35". So I will continue with the 30 amp fuse that the good Samaritan gave me on the road side. I suppose I was lucky the 20 amp lasted as long as it did. And to think I was going to blame the Prince of Darkness for my woes.

 

[CarlS]

Ah, I am glad you found that.

 

[The Seeker]

My T140 will start even with totally dead battery no problem.....but I am still running points & condenser too.

PS: I found a couple Champion N5 plugs finally and have seen a vast improvement over the N3s that the bike is supposed to run.

Posted using Tapatalk 2 via my RAZR

 

[grandpaul]

T120 = N3
T140 = N5

(generally the best solution)

 

[Frank]

Can anyone tell me if I can substitute a different headlight bulb in place of the original 410 bulb? It went out on me last night (in the garage fortunately). I'm having trouble finding an answer to whether I can replace it with something more modern (read: brighter). I'm off the road until I find something.

Is this the right way to ask a question like this or should it go somewhere else?

 

[DaveM]

I am sure you can and I think I remember a conversation about this but don't remember the details. I am sure when one of the other owners read this they would be able to help you

 

[grandpaul]

Change the headlight socket to a modern 3-prong and install a new H4 bulb.

 

[Frank]

Here's another sad story.

I rode my Bonneville to Bass Pro Shop because someone gave me a gift card for my birthday and it was burning a hole in my pocket. Bike was doing fine all the way down. On my way home it started sputtering on acceleration. Then it stalled at a stop light. Every time I had to stop it would stall at idle. I made it as far as my wife's office and stopped to check the plugs. The first plug came right out and looked good. The second plug loosened one or two turns then bound up tight. I thought to myself "that's not good." So I decided to err on the side of caution and we went home and got my truck to haul the bike home.

My biggest worry at this point was that something had broken and was jamming the spark plug in place. So I thought "what a good excuse to take the head off". So I did. It was very educational. Turned out there was just something wrong with the threads on the spark plug. I just had to get it past that one point where it tightened up and it came out fine with no apparent damage to the head.

Every thing else looked good inside too. The pistons have 040 stamped on top. Does that indicate that they are over sized by .040?

Anyway, after cleaning every thing inside I got it back together with no parts left over.

So, back to my original problem of stalling at idle. It turned out I was getting no spark or intermittent spark. The ride had been long enough to rattle some connection loose somewhere.

For the first time I unwrapped the electrical tape from the wire harness and started checking connections from front to back like I should have done a long time ago. I found quite a few suspect connectors. I replaced a few and tightened all the spade connectors. I put it back together and found I had actually solved the problem!

It starts. Even after doing the valve adjustment from scratch. (Never done that before, only checked them for proper clearances.)

HOWEVER, it does start but revs immediately to about 4000rpm and won't slow down. I took the carbs back off and made sure the needles hadn't come unclipped or anything like that. The slides are working well. The float needles are fine (new). I put the carbs back on and it still starts and revs way high. What am I missing? Could I have put something back together wrong? It sounds like all the parts are moving properly, no push rods have tried to escape or anything like that. Could it be a timing issue? I am quite sure it is correct. Would the disassembly have affected the timing? I do get terrible kick back from the kick lever when starting it.

As always, I look forward to any help any one has to offer.

 

[Frank]

By the way, I forgot to mention

My wife and I are going to Barber Motorsports Park in Alabama for the 8th Annual Barber Vintage Festival sponsored by Triumph Dealers of North America! Not only am I thrilled that my wife is willing to go, but we are also camping at the sports park. I am hoping to take my bike with me so I can do a Parade lap, so I have 4 weeks to fix it, not that I want to take that long.

 

[devo]

Sorry Frank,I cant offer anything constructive on the revving issue,tho when you talk about a terrible kick back my first thought is spark timing has advanced itself.
This would also cause high revving,so would be worth checking.
BTW, well done on being able to attend the Barber festival.Make mention of it in the ride out section and you may hear from others who may be attending.Both Carl and GP spring to mind.

 

[Frank]

Thanks Devo. I like your profile picture. My son's email is sodevo83, so when I saw notification of your reply I thought it was him. Are you a Mothersbaugh fan?

I have suspected something is up with my timing for a while. Here's what I know. I put a philips head screwdriver down the port on the back to find the notch in the flywheel to find TDC. I look in the timing inspection plug on the left side cover and make sure the fixed pin points to the line cast in the face of the alternator. Then I make sure I can see the little white dab of paint on the Boyer rotor through the hole in the stator plate. This should be properly timed, right?

 

[devo]

Frank
I've never heard of Mothersbaug but looked him up and can see where your coming from.
My name actually comes from way back and is more related to deviant than to the band.
As for the crank markings etc on your bike I really cant help.I was thinking more of ignition timing.
I am sure AJ (the seeker) or Grand Paul will come to your aid.

 

[otherwise]

Thanks Devo. I like your profile picture. My son's email is sodevo83, so when I saw notification of your reply I thought it was him. Are you a Mothersbaugh fan?

I have suspected something is up with my timing for a while. Here's what I know. I put a philips head screwdriver down the port on the back to find the notch in the flywheel to find TDC. I look in the timing inspection plug on the left side cover and make sure the fixed pin points to the line cast in the face of the alternator. Then I make sure I can see the little white dab of paint on the Boyer rotor through the hole in the stator plate. This should be properly timed, right?

Quote
"I put a philips head screwdriver down the port on the back to find the notch in the flywheel to find TDC."
I don't like the sound of that, a phillips screwdriver with it's point and nonspecific diameter may have you some degrees off. I like to find TDC with a probe down the sparkplug hole, rock motor forward and back again while monitoring the rise and fall of the probe.
The little white dab of paint on the Boyer rotor through the hole isn't properly timed just a starting point to fine adjust from.

 

[Nige W]

Different angle - easy to check... Re-built carbs with new needles may be behaving differently to previous. Check the throttle stop screws (ie back them off a bit and start it up, see what changes) another one is to ensure that the cables are seated down properly in the top of the carbs, another is to make sure that cables/outers are seated properly in the throttle splitter block under the tank.

 

[CarlS]

Unfortunately, finances dictate that I will not get to Barber this year. I hate to miss it. Adrian is going, I think.

 

[grandpaul]

Frank, you have plenty of time before Barber's to get your bike properly tuned.

A timing light needs to be step 1. If you can arrange your layout properly, it's best (when possible) to connect the power to the timing light to a different battery than the one on your bike, preferrably an auto battery (car parked next to the bike). Get alll the tools ready beforehand, loosen the timing plate pillar bolts then finger tight, and set a big fan in front of the engine. A helper is preferred, but you can time a bike by yourself with practice.

Once you have verified proper timing, simply adjust the slide stop screws equally to get the idle lowered.

The probability of me being at Barber's is very near zero. AHRMA required that all prospective Barber's racers must have completeed 2 other races during the season, and I never got out this year; so, why go if I can't race? (1,000 miles each direction)

 

[Frank]

The throttle slides and needles are moving fine. No binding at all. The slide stop screws are backed all the way out. What happens when a carb is worn out? Would it make it rev like this? Also, I know there are two notches in the fly wheel, one marking TDC and the other 38 degrees advanced. Is it possible to get it wrong if I'm also looking at the mark on the alternator lined up with the fixed indicator pin?

Before I took the head off and put it back together the carbs were good.

I'm just afraid of starting it and having it revving to 4000 immediately without it being an obvious fuel problem. And that's what it is doing. I kick it, it kicks me back and then it will usually start on the third brutal kick, but then this crazy revving.

I'm thinking I need to slow it down before I can do the strobe timing. I know I want to check the advance also at 3500 to 4000 rpm, but it's scaring the hell out of me not being able to get a sane idle.

Thanks for your help GrandPaul. (It will be about 7 pm before I can get back to this.)