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XR600 FCR carb clearance, or lack of...

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Hi folks,

I have very nearly finished the re-build of my xr600r engine (wiseco 100mm piston, hotcam, new rod etc.) with only the valves to set and the wiring to plug in. :busted:

I've just gone to fit the FCRMX (off crf450) and the tank is fouling on the throttle cable housing on the side of the carb, I might be able to get the pull cable on but not a chance of fitting the push cable. I've read up on it so I knew this was going to be an issue. The common solutions appear to be:

Heat up the area of the tank with a hot air gun and re-shape

Tilt the carb away from the tank at the top

Now I tried heating up the tank to re-shape it, but all I managed to do was soften the top surface of the plastic, then I got scared :busted: I really can't afford to melt through the tank. Plus I'm worried about making the plastic brittle.

So I tried tilting the top of the carb, this could work but how far over can you go before it causes running problems? It certainly doesn't look right.

Failing this is it a bad idea to just use the pull cable?

Help me before I go back to the original carb!

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It's an on going discussion the Push/Pull cable..My 89 single carb I don't use the push,,not attached due to my using a different type of throttle housing that only takes one cable,..My 80 something XR/XL500/600,,same,..no push cable ..No problems with either.. The push cable in my mind is useless for anything related to "pushing" a jammed slide closed. (The supposed reason for it being there) .Attach a short spring to the carbs actuating arm push cable attachment hole and attach the other end somewhere else appropriate and you have the something I'd call more reliable and solid than the push cable,,Two springs are better than one,,ie the one that woks off the slide actuating arm (standard) and the bodge job one fitted to the push cable hole.,,Redundancy it's called..,Same as a Computer,,have two/three copies of everything you want saved and not all in the same Comp or place.

Course I'm relating my thoughts on other carbs with the push/pull but I think it's relevant whatever carb we're talking about..

Edited by Horri

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I think I see what you mean, however on the FCR the "push" cable does have the effect of forcing the throttle slide closed when you twist the grip to close if, for instance, the return spring should break.

Also if I were to go single cable I would need a different throttle housing on the bars, as mine does not have an integral stop for the grip (it uses the one on the carb).

Appreciate the thoughts though, it would be a lot cheaper to replace the throttle housing/tube than replacing the tank 'cause I'd melted a bloody great hole in it!

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I think I see what you mean, however on the FCR the "push" cable does have the effect of forcing the throttle slide closed when you twist the grip to close if, for instance, the return spring should break.

Also if I were to go single cable I would need a different throttle housing on the bars, as mine does not have an integral stop for the grip (it uses the one on the carb).

Appreciate the thoughts though, it would be a lot cheaper to replace the throttle housing/tube than replacing the tank 'cause I'd melted a bloody great hole in it!

Dunno,,experiment,,Remove pull cable,,Jam something into the slide area..,try pushing the slide closed with the push,,That's my understanding of it's function and it fails miserably to do anything,,Best I can say really.,People have said I don't understand its function correctly,,I say I've looked at the things enough to know the push cable appears to do nothing ,,If it was a solid wire "Yes" maybe it works but not when it's a multi strand wire,,too weak and flimsey for pushing anything other than a feather...

The melting thing I wouldn't be afraid of,,just keep the heat gun moving around the general area and when it's semi soft push things in a bit..

Edited by Horri

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Ahh, I see. The description "push" cable is mis-leading, in effect when you twist the throttle one cable pulls the slide open (the other is at this point in the "push" configuration).

Then when you twist the grip the other way to close the throttle the cables switch roles ie. the original "push" cable is now pulling the slide closed, by acting on the opposite side of the actuating arm, and the original "pull" cable is now being "pushed".

It is kind of difficult to explain, but none of the cables ever do any actual pushing!

Hope this helps.:busted:

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Ahh, I see. The description "push" cable is mis-leading, in effect when you twist the throttle one cable pulls the slide open (the other is at this point in the "push" configuration).

Then when you twist the grip the other way to close the throttle the cables switch roles ie. the original "push" cable is now pulling the slide closed, by acting on the opposite side of the actuating arm, and the original "pull" cable is now being "pushed".

It is kind of difficult to explain, but none of the cables ever do any actual pushing!

Hope this helps.:busted:

Sounds good but to me it simply doesn't work..Leave it with you and the lads for further discussion..Springs doing all the work,,cables are doing very little of anything except the original pull movement.,,Slide drops back down due to the spring,,multi strand thin wire cables haven't got the tensile strength for pushing stuff around..

ie,,

The multi strand throttle cable wires retained by the outer plastic sheathing and the other rounded metal sheathing,,Any looseish part of a multi strand wire not within that sheathing will simply flex at the points not within that sheathing should pressure be applied..,Enough anyway,,better push/pull outa here and do something constructive...water me tobacco..

Edited by Horri

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Hi folks,

I have very nearly finished the re-build of my xr600r engine (wiseco 100mm piston, hotcam, new rod etc.) with only the valves to set and the wiring to plug in. :busted:

I've just gone to fit the FCRMX (off crf450) and the tank is fouling on the throttle cable housing on the side of the carb, I might be able to get the pull cable on but not a chance of fitting the push cable. I've read up on it so I knew this was going to be an issue. The common solutions appear to be:

Heat up the area of the tank with a hot air gun and re-shape

Tilt the carb away from the tank at the top

Now I tried heating up the tank to re-shape it, but all I managed to do was soften the top surface of the plastic, then I got scared :busted: I really can't afford to melt through the tank. Plus I'm worried about making the plastic brittle.

So I tried tilting the top of the carb, this could work but how far over can you go before it causes running problems? It certainly doesn't look right.

Failing this is it a bad idea to just use the pull cable?

Help me before I go back to the original carb!

I installed a motion pro vortex throttle (single pull cable) on my XRL with a 40mm FCR at the beginning of the summer, its been working great and I am very happy with it.

http://www.thumpertalk.com/forum/showthread.php?t=947768&highlight=motion+pro+vortex+throttle

http://www.ebay.com/itm/Motion-Pro-Vortex-Throttle-KX-RM-YZ-WR-CR-125-250-500-/170704805416?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item27becc9e28

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Make to post some pics! Im looking into doing this to my bike as soon as i can afford to get the carb.

How did the carb fit on the intake boot and air box boot?

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I knew that the FCR was problematic on an XR650R, but did not know they had issues on an XR600R. I mounted op an FCR on my XRL and used the OEM XRL cables... mounted up with no problems. The XRL and CRF both use the same or very similar cables and throttle assemblies...

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the xr650l and 600r insulators are slightly different. The xr650l insulator angles the carb a little more down and away from the frame and tank and allows both cables to be used.

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the xr650l and 600r insulators are slightly different. The xr650l insulator angles the carb a little more down and away from the frame and tank and allows both cables to be used.

DO you mean the cable housings? I have a set of CRF cable, XRL cable and XR600R cables and (if I remember right) the only real difference is the actual cable ends are different on the XR600R cables.

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DO you mean the cable housings? I have a set of CRF cable, XRL cable and XR600R cables and (if I remember right) the only real difference is the actual cable ends are different on the XR600R cables.

I think he's talking about the intake to carb boot (insulator).

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Make to post some pics! Im looking into doing this to my bike as soon as i can afford to get the carb.

How did the carb fit on the intake boot and air box boot?

I will take some pictures tomorrow in the daylight.

My carb (off CRF450) was a bargain, £40 + postage off ebay!

The "outlet" of the carb fits straight into the inlet boot, the lip on the carb inlet is filed off. My adapter is a simple machined aluminium tube, 58mm o.d. 54.5mm i.d. 40mm long.

The only real issue has been the fuel tank fouling the cable housing.

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I will take some pictures tomorrow in the daylight.

My carb (off CRF450) was a bargain, £40 + postage off ebay!

The "outlet" of the carb fits straight into the inlet boot, the lip on the carb inlet is filed off. My adapter is a simple machined aluminium tube, 58mm o.d. 54.5mm i.d. 40mm long.

The only real issue has been the fuel tank fouling the cable housing.

Odd indeed... I didnt realize that the XRL and XR600R tanks were that much different. An FCR fits on an XRL with no interference whatsoever.

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!

The "outlet" of the carb fits straight into the inlet boot, the lip on the carb inlet is filed off. My adapter is a simple machined aluminium tube, 58mm o.d. 54.5mm i.d. 40mm long.

There-in lies the problem ... your inlet (to the engine from the carb) adapter needs to have a downward slope/bend. A straight inlet is causing the problem. If you have a sloped/bent inlet adapter (which will put the carb down lower) you won't have to worry about the tank interference.

:busted:

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I also fitted a FCRMX carb to my xr600r.. there was only one way it would fit.

Also, I think I used CRF cables and a modified xr600 gas handle.. Will fit a crf gas handle in the future..

Used the stock intake manifold and used a piece of thin walled tubing and a piece of silicone hose for an adapter between the filter housing manifold and carb..

Carb is working out GREAT! I was amazed it ran really well with just a 152 main jet. The old carb had 168... You would think that those would stay the same, but apparently somehow the FCRmx gives more fuell when wacked open... or my bike has been running lean for quite some time and I don't notice... :busted:

Made a thread of it here on Thumpertalk (with pics)

http://www.thumpertalk.com/forum/showthread.php?t=980342

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There-in lies the problem ... your inlet (to the engine from the carb) adapter needs to have a downward slope/bend. A straight inlet is causing the problem. If you have a sloped/bent inlet adapter (which will put the carb down lower) you won't have to worry about the tank interference.

'Red is right, the XRL inlet boot (or insulator) angles the carb further down and away from the tank.

As far as cables, the XRL cables/twistgrip work perfect with the fcrmx, you just need to route them on the right side of the frame like they are on the xrl.

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'Red is right, the XRL inlet boot (or insulator) angles the carb further down and away from the tank.

As far as cables, the XRL cables/twistgrip work perfect with the fcrmx, you just need to route them on the right side of the frame like they are on the xrl.

I have a Xr600R, not an L,and it fit's tough it's a tight fit. See my Thread. :lol:

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I am in the same situation, trying to fit a fcr on my 600r.

What did you do? heat the tank? relocate the throttle assembly?

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