Fuel Pump Bypass?? Maybe possible?

[capitanoinsano]

I am curious if I can keep a little piece of pipe or hose with barb fittings to bypass the fuel pump on long trips (in case it goes out), on my 89 FJ1200.  I would think it would work to get me home as the earlier models had no pump.  ONLY ISSUE is that the float valves in the carburetors had smaller openings (I think to reduce pressure) on the models with fuel pumps.


According to parts diagrams the 86-87 had the same carbs (bodies etc) as the 89,90.  I think the only difference is the size of opening in the float valve and needle (well... and jetting and nozzles possibly too were different on 89/90 vs 86/87).  I know the 91-93 had a different carburetor body, but I think were jetted about the same as the 89/90 and used the same float valve as 89/90.

Anyway... So if my fuel pump were to go out on the road I could bypass it and maybe it would run fine.  Or maybe I would have to pull the carbs and install 86/87 float valves to get home without a fuel pump.  That would be more of a hassle, but feasible.

Any opinions or experience with this?

[RichBaker]

Its been done by several of our members.... they report that as long as you don't try any extended high speed running, it works great. Freeway droning will get you home easily....

[thuber3040]

Curious what changed from 84/85 on that the first yrs did not need the fuel pump, is it carb design or tank shape?
You could put a small inline pump on a relay so it shuts off with ignition if the factory one fails and its too expensive, although the facet? ones have gotten pricey also

[racerman_27410]

Curious what changed from 84/85 on that the first yrs did not need the fuel pump, is it carb design or tank shape?

Tank venting was an issue on early models along with a bit of vapor lock/heat soak in the carbs on really hot days....... the fuel pump was a logical solution to just overpower the problem.

the only difference i can see between the early and late model carbs (besides the size of the float valves) is the size of the metal fuel inlet tubes between the carbs. The fuel pump models are considerably smaller.


Kookaloo!

[capitanoinsano]

I'm thinking the dominant restriction would be the float valve hole.  I'm glad to hear someone else has thought of this and tried it out.  I think an FZ1 pump may work if an elbow fitting were added to one line.  There is some Airtech pump that I read works (in a thread), but fittings are different and in different locations.  I've never seen a pic of one installed.

As far as differences from fj1100 carbs.  Mostly the changes were just fine tuning the previous design (jetting, nozzles etc).  The FJ1100 is a different engine and had different needs (slightly).  But I know from experience that FJ1100 carbs (and bikes) had a nasty tendency to develop a hanging idle.  The vacuum would actually pull the butterfly open on the far left carb because it was the easiest butterfly to open.  Less spring force holding it shut.  They may have even changed size and location of the bypass holes in mouth of carbs.  It would not surprise me if 86/87 FJ1200 carbs are an improvement for an fj1100.  I think the pilot air jet was changed too.

Pilot jets were too small on all years.  Emissions rules probably made factory jetting progressively worse.  All I know is in stock form I felt that the 86/87 model was the quickest of all.  But some tests say the fj1100 was.

[Arnie]

capitanoinsano,

The fuel pump is very reliable and rarely goes out.  That said, mine did (at ~110,000 kms).  I was able to do a bypass tube like you're suggesting, and it worked OK for freeway droning with a 1/2 + full tank.  I did find another low-pressure fuel pump at an auto parts shop that I paid too much money for. bit could have made it home without trouble if necessary.  This was with the late model float valves.

If you want to use an FZ1 fuel pump, make sure its from a carb'ed bike.  The FI pump is way too much pressure.

Cheers,
Arnie 

[SlowOldGuy]

As far as differences from fj1100 carbs.  Mostly the changes were just fine tuning the previous design (jetting, nozzles etc).  The FJ1100 is a different engine and had different needs (slightly).  But I know from experience that FJ1100 carbs (and bikes) had a nasty tendency to develop a hanging idle.  The vacuum would actually pull the butterfly open on the far left carb because it was the easiest butterfly to open.  Less spring force holding it shut.  They may have even changed size and location of the bypass holes in mouth of carbs.  It would not surprise me if 86/87 FJ1200 carbs are an improvement for an fj1100.  I think the pilot air jet was changed too.

HUH?
I know from 24 years experience that my '85 carbs have none of those problems..  What are "bypass holes?"  The carb bodies are all the same.  The California emissions models had an extra vacuum port on #2 and #4 (I think), but that was the only exernal difference.

On the fuel pump models, they changed fuel the plumbing from a dual inlet to a single inlet between #2 and #3, but the the early models had the same bosses in the casting, they just weren't drilled.  Some slight jetting changes were implemented over the years, but only a single jet size, nothing significant.  When I bored my 1100 to a 1200, I didn't have to change any of jetting or the needle position.

DavidR.

[capitanoinsano]

The bypass holes are the 3 tiny holes arranged in a triangle a bit behind the mixture screw tip opening.  The first bypass hole is mostly covered up by the butterfly at idle position.  The second hole is completely covered by the thickness of the butterfly, and the rear hole is open to the air path behind the butterfly at idle.  As the butterflies are opened one by one the holes are exposed, getting more pilot circuit air fuel mix to the engine.  They are also called transition ports as they give some more air/fuel flow till the slide lifts allowing the main jet and needle to contribute.   I had an 85 fj1100 and worked on someone else's 84 (I think) fj1100, and both did it.  I think Dynojet had some alternative idle air jets to help the lean spot off idle.  The carb bodies of the 84,85 are different castings than the 86-90.  The 91-93 are different yet.  Mostly they are the same.  My 85 gave me fits with the hanging idle.  Mechanics said I was trying to be too much of a perfectionist, just ride it.  I even tried stiffer linkage springs (not butterfly springs, the ones that preload the synchronization screws and attach butterfly linkage.  That helped some, but there was a slight surge off idle when warm, and could never quite get rid of it.  I went up 3 pilot jet sizes, no help.  I tried 2 other sets of carbs, same thing.  Valves set perfect.  Never quite solved it but if I tried again I would probably take a tiny drill bit and open up the first bypass holes a little.  Later I found a person I know had the same problem with an 84 FJ1100.  I tried synching carbs, tuning etc, and got it better, but never gone.  A year or 2 ago I read that this was a common problem with the fj1100 carbs, not sure why.  But a lean spot off idle was claimed to be the culprit.

[SlowOldGuy]

The bypass holes are the 3 tiny holes arranged in a triangle a bit behind the mixture screw tip opening.  ...  They are also called transition ports as they give some more air/fuel flow till the slide lifts allowing the main jet and needle to contribute. 

Okay, I know what you're talking about.  I know those as progression ports.

 I had an 85 fj1100 and worked on someone else's 84 (I think) fj1100, and both did it.  I think Dynojet had some alternative idle air jets to help the lean spot off idle.  The carb bodies of the 84,85 are different castings than the 86-90.  The 91-93 are different yet.  Mostly they are the same.  My 85 gave me fits with the hanging idle.  Mechanics said I was trying to be too much of a perfectionist, just ride it.  I even tried stiffer linkage springs (not butterfly springs, the ones that preload the synchronization screws and attach butterfly linkage.  That helped some, but there was a slight surge off idle when warm, and could never quite get rid of it.  I went up 3 pilot jet sizes, no help.  I tried 2 other sets of carbs, same thing.  Valves set perfect.  Never quite solved it but if I tried again I would probably take a tiny drill bit and open up the first bypass holes a little.  Later I found a person I know had the same problem with an 84 FJ1100.  I tried synching carbs, tuning etc, and got it better, but never gone.  A year or 2 ago I read that this was a common problem with the fj1100 carbs, not sure why.  But a lean spot off idle was claimed to be the culprit.

We go through phases where several people have reported a high idle problem.  Varies with the year model.  Of the owners that have fixed this problem and reported back, it is usually attributed to an air leak somewhere (intake o-ring, cracked/leaking intake manifold, vacuum cap, boost sensor leak, petcock diaphragm leak, etc.) or a stuck/sticking/maladjusted throttle cable.  In all the years I've been associated with this group, this is the first I've heard of it being specifically an '84/'85 model problem. 

Were you the original owner of your FJ?  Is it possible that a previous owner screwed something up?  I ask because I've never experienced anything like what you're describing and I'm pretty sure neither Pat nor Lee have had this problem either.  We are all longtime owners of 1100s. 

Please don't take this personally, I'm just trying to clarify the difference between "It happened to me" and "ALL of them do this."  Given the amount of "fixing" you did that didn't really cure the problem, perhaps you were fixing the "wrong" problem?  Again, maybe something a previous owner induced?  Changing 3 idle jet sizes and trying 2 other sets of carbs without affecting the symptom would indicate to me that the problem was somewhere else.

That probably reads kind of rude, but it's not meant to be.

DavidR.

[andyb]

I'm thinking the dominant restriction would be the float valve hole.  I'm glad to hear someone else has thought of this and tried it out.  I think an FZ1 pump may work if an elbow fitting were added to one line.  There is some Airtech pump that I read works (in a thread), but fittings are different and in different locations.  I've never seen a pic of one installed.

Pulled from my big book of notes:

You have to use the fuel pump from a 1999-2002 R6 as the 2003+ fuel pump is a plastic, submerged type. As near as I can tell, the R1 fuel pump is exactly the same and should work as well (same years).....however I have not confirmed this. You have to take off the ounting bracket that is around the R6 pump and use the existing FJ mounting bracket. The wiring plug is exactly the same and plugs right into the existing plug on the FJ. The intake and output tubes, instead of coming straight out like on the FJ pump, turn at a 90? angle. Also the "fuel in" tube on the R6 pump is for a larger inner diameter fuel hose than the hose that comes stock on the FJ. You can stretch out the FJ hose and get it on there; I did that and it worked. However, I didn't feel good about doing that so I replaced the fuel line coming from the petcock to the fuel pump with 5/16" fuel line that I bought at an auto parts store.
You can use the existing fuel line from the pump to the carbs as that "fuel pump output tube" is the same size as the existing FJ tubing. That is the only difference. keep in mind that I am NOT using an airbox. This is where the 90? angle comes into play. I don't think that you would have any problem routing the fuel lines while using the stock air box....but I have not confirmed this. Also, the 1997-2002 YZF600 Fuel Pump is IDENTICAL to the fuel pump on the FJ.

Dunno who said it though, but while digging through archives I found that and just saved it (saved a bunch of useful info that way).

[Marsh White]

I wrote that.  I posted this on September 15th 2004 on the Yahoo forum.  Here is the whole post:
(note: if I had to do it again I would have searched out the YZF600 fuel pump mentioned at the bottom of this post)

using an R6 fuel pump on an FJ1200

Well guys, I finally received an R6 fuel pump from ebay and successfully
mounted it to my 89 FJ. It works like a charm! They are all over ebay for
cheap from kids wrecking their R6's. In fact I bought two for the exact
same price from different people: $30.50 to my door. You have to use the
fuel pump from a 1999-2002 R6 as the 2003+ fuel pump is a plastic, submerged
type. As near as I can tell, the R1 fuel pump is exactly the same and
should work as well (same years).....however I have not confirmed this.

You have to take off the mounting bracket that is around the R6 pump and use
the existing FJ mounting bracket. The wiring plug is exactly the same and
plugs right into the existing plug on the FJ. The intake and output tubes,
instead of coming straight out like on the FJ pump, turn at a 90? angle.
Also the "fuel in" tube on the R6 pump is for a larger inner diameter fuel
hose than the hose that comes stock on the FJ. You can stretch out the FJ
hose and get it on there; I did that and it worked. However, I didn't feel
good about doing that so I replaced the fuel line coming from the petcock to
the fuel pump with 5/16" fuel line that I bought at an auto parts store.
You can use the existing fuel line from the pump to the carbs as that "fuel
pump output tube" is the same size as the existing FJ tubing. That is the
only difference.

Keep in mind that I am NOT using an airbox. This is where the 90? angle
comes into play. I don't think that you would have any problem routing the
fuel lines while using the stock air box....but I have not confirmed this.

Pics Here: http://www.fjowners.com/index.php?topic=1147.0

Also, the 1997-2002 YZF600 Fuel Pump is IDENTICAL to the fuel pump on the FJ
(thanks to George Bowwers for this info).

[andyb]

Ah well, there ya go.

[capitanoinsano]

The carbureted FZ1's should work then maybe.  The FZ1's of 2001-2005 had the 99-03 R1 engine and similar carbs, probably same pump.  I have a 2003 FZ1...hmmm, I guess there's always a spare one there.

[SlowOldGuy]

Just a small correction.  The '02 and '03 R1 had a first gen hybrid vacuum piston fuel injection system.  Looked like CV carbs but was actually FI.  I wouldn't use the pump.  Besides, I think it was in the tank.

DavidR.