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Ageing Vacuum Lines on a GL1500

5072 Views 8 Replies 6 Participants Last post by  Graham B
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I’ve been searching the archives and I haven’t run across what I need. My 1989 Goldwing with 35,000 miles has developed a problem and I think maybe a second symptom that is related. About three weeks ago I noticed that when I would let off the throttle the RPM’s would not fall like they should. They fall to about 2,000 to 2,200 RPM and just hang there for three or four seconds then slowly drop to idle.

I have also noticed that the cruse control seems to wonder up and down more that it use to. It seems to want to run around 70 to 72 MPH no mater what speed I set it to. I don’t think that would be a very good defense in court so I have to use it much less lately.

I was at Wing Ding 31 in Tulsa last week and talked to Stu in his seminar and his diagnosis was collapsing and/or leaking vacuum lines. I stopped by the local Honda Dealer and spoke with the shop foreman and he provided a schematic of the vacuum lines and I looked at a GL1500 that was in the shop getting the very same thing done to it. Looks like a major teardown and I’m not looking forward to it. I asked how much to have them do it for me and he told me that they weren’t allowed to take in any bike older than a 1993. He also said that they had waited for three weeks for some of the lines to come in for the bike they were working on.

OK, here is my question:

Does anyone know which lines on that age of bike are the problem lines?

I would like to get them on order before I take the bike apart. I really hate the idea of it being laid up for a month or so. I’m planning a cross country trip in September so I need to get this addressed soon.

Thanks for any and all help.

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hi n5hq god only knows what hoses would be gone my guess and the one that causes the most probs is the main one on the left vacume port it has a sharp bend in it as is knowen to split with time as for the hoses them selfs there is nothing special about the hoses you can buy the lenght you need in an auto store of the differant sizes you need
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Those hoses are pre-bent to hold their shape and have rather sharp bends in them. That's what makes them special.

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I looked at some of the hoses that were taken off the bike they were servicing and there is just no way a stright vacuum line could be used. It also seems that every hose was a different diamature. There were some very sharp bends and from what I saw not much room to take the long way around a corner.

I'm sure some of the hoses can be from the local auto parts store but with my luck those hoses will be fine. It will be the ones I have to wait three weeks for that will be the bad ones. I was just hoping that someone had some incite on the ones that are more likely to be needed. I hate to order the complete set. I would rather get a new bike. Hey, not a bad idea!

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If you need to bend vacuum lines at sharp angles, you can put a spring inside the hose to keep them from collapsing.
This is what I would do.
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I think I'd be balancing the carbs before I went too far with the hoses.
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Well i had to replace almost all my vaccum lines on my 93 1500. You are right its not a easy job.
I bought all my hoses at the local NAPA store.
I will also advise you to check the needle vacuum slides oneof mine was split about 8 different places. I had to pull my carbs to change it.
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I had an appointment today for a diagnosis with a Honda dealer. The mechanic didn’t have the manual for the 1989 so he was working from a 1988 manual. He admittedly was a GL1800 mechanic but he had resources. He tore it down to the carbs and couldn’t find anything wrong. One vacuum line was a little soft in a bend but wasn’t bad. He just cut about a half an inch off and it was fine. The vacuum slides were in perfect condition. He just couldn't find anything mechanical wrong.

He thinks it is electrical but the controls and connectors are under the carbs so he didn’t go any further. He spent over three hours and only charged me for one. He ordered a 1989 manual and will confer with senior techs before I bring it back for more troubleshooting.

I did notice another symptom on the way home. I can’t even begin to understand how this is possible but if I hold the clutch and shift from second to third the RPM’s will increase about 1K RPM and when I shift back to second the RPM’s will fall to idle. I had no idea that there were sensors to detect gears other than neutral.

He told me that he had a few other 1500’s that were acting the same and he wanted to figure it out since he thinks it may be a common problem. He stated that he will spend some of his own time researching. I will be taking the bike back later and leaving it so that he can tear it down, remove the carbs and figure this thing out.

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From someone who didn't believe that a vacuum line could cause all those seemingly different problems, believe me when I say it's probably the lines. Also, using non Honda lines may be a false economy. I did that and I now have lines on order.

To be fair, it's the smaller lines that seem to be more vulnerable. I have them on order at the moment as the non Honda ones can't take the heat or pressure. Just don't forget the tube that between the manifolds - nicely kept out of sight under the heat protector.

Try this website to find the parts

Also, the tubes I have ordered (and it's not all of them) are;

Description Detail Part Number[/b]
No 1 tube (ORN)Manifold link to ECU 17173-MN5-000
No 3 tube (ORN) Manifold link to ECU 17175-MT2-000
No 5 tube (ORN) Manifold link to ECU 17462-MT8-000
No 1 tube From air injection control valve 17358-MT8-000
No 1 tube From A1CV solenoid valve “T”
piece to metal connector near
engine 17350-MT8-000
Un-numbered tube From A1CV solenoid to “T”
piece (short) 17351-MT8-000

Also, to save yourself a lot of other problems, when was the last time you changed/cleaned your sub air filter?
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