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Author Topic: Fuel System questions  (Read 1693 times)
MikeCr
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« Reply #15 on: October 14, 2016, 07:11:58 PM »

Got the JIS screwdrivers today.  They do make a huge difference. 


Mike
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a_morti
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« Reply #16 on: October 14, 2016, 08:06:22 PM »

Preach, brother Smiley
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MikeCr
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« Reply #17 on: June 25, 2017, 01:46:46 PM »

Finally got everything back together about three weeks ago and I've been struggling with it ever since.  It just won't run.  The first time I started it after reassembling it it took a while to get it to stay running but it eventually did.  But ran rough under 5K or so and wouldn't idle worth a damn.  A week later when I looked at it again and every time since it just won't run above idle for any amount of time.  This bike always was very cold blooded like most bikes of the period were but nothing like this.  I've done everything I can think of to get it to run right.  I think it's time to just cut my losses and sell it.
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Sugs
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« Reply #18 on: June 25, 2017, 02:05:01 PM »

Did you remember to attach the vacuum line from the upper left side of the crankcase?  Easy to forget as its kinda hidden under the engine to frame mount.
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1979 Honda GL1000 Goldwing - 1990 Honda CB1
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« Reply #19 on: June 25, 2017, 02:08:49 PM »

Also, my bike likes the clutch pulled in when I go to start it regardless of whether its in neutral or not.  Just something to try.

Where are you located BTW?
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MikeCr
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« Reply #20 on: June 25, 2017, 02:24:34 PM »

Not sure which line you're talking about.  As far as the clutch, never had a problem with that before.  I'm in the Milwaukee area.


Mike
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a_morti
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« Reply #21 on: June 25, 2017, 04:02:25 PM »

Did you remember to attach the vacuum line from the upper left side of the crankcase?  Easy to forget as its kinda hidden under the engine to frame mount.
There's no vacuum lines on the CB-1. There is a crankcase vent from the rocker cover but it's just a vent.

Strange that it's the upper range not working, blocked carbs usually would influence the small channels to do with low speed running.

Could you have a perished carb diagram, not lifting one or more of the slides?

The old favourite is remove the spark plugs for a clean, but I'm not so sure. They'd usually work or not work.
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ModerateFkr
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« Reply #22 on: June 25, 2017, 11:10:04 PM »


This issue of CB-1s not running after rebuilds and long periods of not being ridden is fairly common isn't it? And the symptoms and problems seem varied. Nasty old fuel in carbs and deteriorated rubber components seem to often be the culprits, causing everything from air leaks to sticking parts. They really don't like being left unused.

When I do my renovation over the winter, I'm planning to unbolt the front engine mounting arms from the frame and try to drop the engine complete with carbs. Then I'll mask everything I don't want to paint, and run the engine on a rig to try and keep it in the game.

Sorry I can't offer any more help than this MikeCr. Hope your frustrations end soon bro. Don't give up. It's fuel, rubber or electrics. Hondas don't have gremlins :-)
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MikeCr
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« Reply #23 on: June 26, 2017, 08:24:20 PM »

Well it's running.  Not happy with the way it is at low revs but at least I've got something now.  Still not exactly sure what's going on but I have an idea.  The last thing I did was button up the air box and then I realized I had not tightened the clamps for the boots between the carbs and the air box.  After doing that and after just a minute or so it started. 

I tried running it both with the air box closed up and with it open or even off as I was trying to figure out what was wrong.  I don't remember though how it ran in every case.  Now I'm wondering if my problems were because of not having it sealed up.  At first I was thinking it wouldn't matter other than running a little leaner with the cover off.  After I got it to run late yesterday a thought occurred to me.  There are tubes on the intake side of the carbs that extend into the air box so maybe running it open like that was a problem.  The problem is that I had it running several times over the course of the last few weeks and I don't remember what configuration it was in each time.

Now that I've got it running I can try to tweak the idle mixture to see if that will help with the way it runs at the low end, especially the transition from idle.  The bad thing is it's just about impossible to get at the screws for the inner two carbs.  And according to the manual you have to take the carbs off and separate them to get the limiter caps off the inner two.  There's no way I'm doing that!  I may have to just be satisfied with the way it is.  The good news is that most of the time the engine will be at 5K or better.  We'll see.


Mike
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ModerateFkr
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« Reply #24 on: June 26, 2017, 08:39:25 PM »

Well it's running.  Not happy with the way it is at low revs but at least I've got something now.  Still not exactly sure what's going on but I have an idea.  The last thing I did was button up the air box and then I realized I had not tightened the clamps for the boots between the carbs and the air box.  After doing that and after just a minute or so it started. 

I tried running it both with the air box closed up and with it open or even off as I was trying to figure out what was wrong.  I don't remember though how it ran in every case.  Now I'm wondering if my problems were because of not having it sealed up.  At first I was thinking it wouldn't matter other than running a little leaner with the cover off.  After I got it to run late yesterday a thought occurred to me.  There are tubes on the intake side of the carbs that extend into the air box so maybe running it open like that was a problem.  The problem is that I had it running several times over the course of the last few weeks and I don't remember what configuration it was in each time.

Now that I've got it running I can try to tweak the idle mixture to see if that will help with the way it runs at the low end, especially the transition from idle.  The bad thing is it's just about impossible to get at the screws for the inner two carbs.  And according to the manual you have to take the carbs off and separate them to get the limiter caps off the inner two.  There's no way I'm doing that!  I may have to just be satisfied with the way it is.  The good news is that most of the time the engine will be at 5K or better.  We'll see.


Mike

Well done Mike. You're part way there. It's a carb setup or air leak issue by the sound of it.

Well worth taking notes when trying different ways to solve an issue. I lost the tail cowl bolts two days ago. All I had to do was screw them back into the frame while I worked on the thing. But I first put them in the tool tray. Then I decided to put them somewhere 'safe'. Idiot!! Took me 2 hours to find them - in the manual folder!

It's not just us oldies who can't remember stuff.
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Sugs
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« Reply #25 on: June 27, 2017, 01:50:28 AM »

There's no vacuum lines on the CB-1. There is a crankcase vent from the rocker cover but it's just a vent.

There is on my bike, whole vacuum apparatus that resides under the carbs.

See this link: http://www.partzilla.com/parts/search/Honda/Motorcycle/1990/CB400F+AC/AC+AIR+SUCTION+VALVE/parts.html

Possible its California specific, but my bike acts just like MikeCR describes when that line is disconnected.  He may want to check and see if he has this stuff under the carbs.

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« Reply #26 on: June 27, 2017, 06:05:08 AM »

There's no vacuum lines on the CB-1. There is a crankcase vent from the rocker cover but it's just a vent.

There is on my bike, whole vacuum apparatus that resides under the carbs.

See this link: http://www.partzilla.com/parts/search/Honda/Motorcycle/1990/CB400F+AC/AC+AIR+SUCTION+VALVE/parts.html

Possible its California specific, but my bike acts just like MikeCR describes when that line is disconnected.  He may want to check and see if he has this stuff under the carbs.


Ok, could well be cali spec. Does yours have little chrome pipes around the cylinder barrels?

The cali spec is a fair bit leaner. Maybe it's possible to put it to 49 state spec?
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« Reply #27 on: June 29, 2017, 05:41:35 AM »

Before you start messing with the mixture screws (which should 2-2 1/2 turns out) have you syncronised the carbs? You'll need a set of gauges or one of these https://www.carbtune.com/ which are really easy to use.

Alternatively you get fairly close using a very small drill bit. Adjust the idle screw until carb no.3 (or it might be 2 can't remember) until the butterfly just grips the drill between itself and the body then do the same for the other carbs using the idle adjuster screws - this will get you near enough.

Also with low revs, It is usually the slow jet that could still be blocked rather than the main jet
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MikeCr
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« Reply #28 on: July 15, 2017, 07:46:32 PM »

Finally think I'm getting somewhere with this.  It's been iffy all along as to whether it would even start.  This morning I tried to start and had no luck.  But then I remembered that a few times when I left it sit for 20-30 minutes it would fire up. making me think that it was just too rich on the low end.  I came back to it later in the day today and tried a couple of things.  First I tried starting it without choking it all all, that didn't work despite it being about 80 degrees here.  Then I thought what if I choke it and crank it for a few seconds and then take the choke to about the halfway position.  Fired right up!  So clearly the low end is too rich which is also most likely why the idle and transition is so bad. 

I can try adjusting the idle mixture on the outer two carbs and see if it helps, not sure where I left them the last time I played with it.  The inner two though are completely inaccessible.  There's no way to get a screw driver on them, I might be able to get a needle nose or forceps on them but those stupid limiter caps will be a problem.  According to the manual the only way to get the screws out and remove the limiter caps is to remove the carbs from the bike and separate them.  There's no way I'm doing that again.  It was enough of a PITA the first time.

As far as carb synch, no.  If it was required I wouldn't do it, I'd have to take it in somewhere.  I don't have the equipment, the expertise or the patience to do it.  But I seriously doubt it would make a difference.  Number one I never changed anything that would make a difference in the relationship between the butterflies, number two when the throttle is fully open to my eye they're all in the same plane and number three when the throttle is fully closed they all touch the bore at the same time.

So I'm going to play around with the idle mixture and see if I can get it to run better at the low end.  It's rideable the way it is, especially since this bike doesn't spend much time below 5K anyway.


Mike 
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ModerateFkr
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« Reply #29 on: July 15, 2017, 10:02:48 PM »

How difficult are those inner carbs to access? I haven't had a really close look yet. The reason I ask is that Carbtune sell a 90 degree gearbox screwdriver they says has zero backlash.

http://www.carbtune.co.uk/bevel.html

I found it when I noticed Carbtune Pro 4 available new for a wide range of prices on eBay.

It's often the case here in the UK that manufacturers won't sell their products directly to the public, or they use official wholesale distributors, and quote silly RRP prices that are always discounted by official retail outlets. Carbtune are different. They sell direct from their website. And you get the pouch included for... LESS than anyone on eBay!!!

I'm not a representative of Carbtune, indeed I learned of them from one of you guys only very recently - but I'm working on a free pint of Guinness next time I'm in Belfast Wink

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