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Old 12-02-2009, 01:24 PM   #16
InfiniteMiles
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Nice work. My guess is the spacer plate is there to reduce bog when going when quickly going to WOT, but don't quote me. I've only ever seen those on two strokes to change the power band.


Beautiful Hawk as well.
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Old 12-02-2009, 02:17 PM   #17
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It bolts directly to the cylinder head on my 350. Different animal, but same setup...
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Old 12-02-2009, 09:20 PM   #18
Ghost_Mutant
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insulator/manifold details

Quote:
Originally Posted by Duff Man
December 2/09


Notice here on the engine there is a aluminum spacer plate between the carb boots and the cylinder. Question: Is this stock, or is this a reducer plate that is used on some bikes (I know it is used on cars) to make the intake holes a little smaller which increases the speed of the air/fuel going into the engine ?? It's not pictured on the exploded view of the engine, which makes me think it may have been added after the fact?


Exploded view. . no spacer plate
Very interesting difference there between my XR5 and the XL6. I have a factory heat insulator plate on both my XR5s (83 and 84). It's not aluminum, but it is a phenolic type of insulator. I suppose it's to help keep the carbs from getting too warm, but I would have guessed that the rubber in the manifold would be enough by itself. Apparently on the XL6 it is enough, since that's what the manual shows. I have bought a carb manifold/insulator for the XR6 with the dual carbs off of ebay. It also has the extra phenolic plate.

I'd say your plate is not stock, but I'm surprised to learn the XL6 does not have the phenolic type. The stock plates on my bikes have machined grooves for O ring sealing. It should be interesting to learn what your aluminum plate has for sealing to the head.

See here for XR5 head parts:
http://www.cmsnl.com/honda-xr500r-84...t/E++0201.html
The insulator plate is part #9.


Two more things:
1) I asked a question about the reed valve on the XL600 thread. No reply yet. So I'd be curious to know if your 85 has the valve. It's shown in your parts diagram in the upper, center left of the diagram. It's the parts surrounded by the rectangle. It's located in a separate and sealed chamber in the valve cover.

2) Your insulator has a MG3 part code. This is the code for the 83 XR5, and I would have thought that Honda would have changed this to a newer type by 85. When you get your insulator off the head, check to see if it has a cross port machined in it. The diagram shows the 83 insulator/manifold without the machined cross port. Read section 19 of the manual to see how the reed valve worked as designed, and the 83 needs the valve/head cross ports if it lacks the cross port in the manifold. It's on page 19-3 on my 84 XL6 manual pdf.

It's my understanding that Honda dropped the reed valve for the XR6. And to do this the machined cross port in the insulator/manifold is required (to keep the secondary valve cool during idle and part throttle conditions when the secondary carb is closed).

I want to eliminate my reed valve because it's a source of oil burning if the valve cover gasket leaks. That's why I bought the XR6 manifold for my 83 XR5 rebuild to replace my stock MG3 manifold.

Now I'm trying to figure out the best way to plug the reed valve holes/ports that are in the top of my XR5 heads.

See here for Honda codes:
http://www.oscarmayer.net/atc/manuals/honda_tips/UNDERSTANDING_HONDA_PART_.PDF

http://www.cmsnl.com/faq.php?fq_catid=14
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Old 12-03-2009, 05:46 AM   #19
brucifer
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That intake plate looks home made to me.
You can tune an engines power characteristics by shortening or lengthening the intake tract. Was that being tried here? Don't know if that little bit would change anything. Are the holes the same diameter as the ports?
Here's one. Maybe the carb to airbox boots shrunk up and the PO fixed that problem with the plate.
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Old 12-03-2009, 08:16 AM   #20
Ghost_Mutant
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Quote:
Originally Posted by Ghost_Mutant
See here for XR5 head parts:
http://www.cmsnl.com/honda-xr500r-84...t/E++0201.html
The insulator plate is part #9.


It's my understanding that Honda dropped the reed valve for the XR6. And to do this the machined cross port in the insulator/manifold is required (to keep the secondary valve cool during idle and part throttle conditions when the secondary carb is closed).
I should have added a little more info. Here is a link to the 85 XR600 exploded head diagram:
http://www.cmsnl.com/honda-xr600r-85...ist/E++02.html

Note that:

1) reed valve is missing
2) phenolic plate is between the carb insulator and the head (part #7)
3) carb insulator/manifold/rubber boot has the machined cross port (part #6)
This newer style carb manifold requires a special, longer sealing o-ring (part #14)
However, the part code for this carb manifold is 16211MG3010, note the MG3.

I'm going to guess that you have this manifold on your 85 XL600. Now, I'm very curious to know if you also have the reed valve on the top of your cylinder head.

When I bought my original 84 XR500 it was smoking on startup. I thought this was for the usual reasons, like stem seals and rings. But when I pulled the carb manifold off, I saw substantial carbon buildup on the secondary intake valve, but the primary was clean. A leaking valve cover gasket was allowing oil to get in the combustion chamber through the open hole above the secondary intake port. This is part of the reed valve setup/system.

Previous owner didn't deal with it right away, and the secondary intake valve and guide were shot from the carbon buildup, but the primary was still good.

Since Honda removed the reed valve in the 85 XR6 and just went with the machined cross port carb manifold, this is how I'm going to build my two XR5s.

I had been asking around to see if any of the XL600 owners had done the same thing (get rid of the reed valve).
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Old 12-03-2009, 08:52 AM   #21
ppe172
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I had one of these ('85) that I sold last year. The '85 does not have the reed valve. It was dropped for either the '84 or '85 model year. You are right about the cross port manifold. The '85 (and I believe all XL600s) does have the phenolic spacer, and the later ones have the cross port machined in. They are discontinued, I had to buy one off eBay, so if the PO needed one he probably had to make one. However, my understanding is that it is a heat insulator, something which an aluminium spacer would definitely not be, so I don't know if that was a good choice.
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Old 12-05-2009, 08:29 AM   #22
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Quote:
Originally Posted by ppe172
However, my understanding is that it is a heat insulator, something which an aluminium spacer would definitely not be, so I don't know if that was a good choice.
My 1983 dual-carb XL600R's plate looked like some brittle brown plastic. Not sure if it started that color, or it heat/oil turned it that way. Last time I had it apart, I learned it doesn't fit in backwards, and spent a long time staring at it while I tried to get the bolts started.
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Old 12-05-2009, 11:19 AM   #23
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Quote:
Originally Posted by ZapGuy
My 1983 dual-carb XL600R's plate looked like some brittle brown plastic. Not sure if it started that color, or it heat/oil turned it that way. Last time I had it apart, I learned it doesn't fit in backwards, and spent a long time staring at it while I tried to get the bolts started.
It would seem that all the evidence is pointing to a mistake in the 83-84 XL600 service manual. I just looked through my copy again and I didn't see the heat insulator in the diagrams or photos. Did I miss it?

Keep in mind that the 83 does not have the machined cross port in the carb insulator (manifold). And just to be clear, none of my heat insulators (the plate we're discussing here) has the cross port, it's just a piece of phenolic type plastic that has O ring grooves on one side (I've got three or four of them). The cross port upgrade showed up in 84 and later.

Yes, I'm going off of memory here, my parts are currently in boxes in the attic. If I get a chance I'll pull them out to make sure I'm reporting accurate information.

Here is the download link for the manual again:
http://www.hondaxl.it/manuali.htm

Head stuff is in part 6/6b.

I've noticed some mistakes in my XR500 factory Honda service manual as well. More stuff to make wrenching on the older bikes more interesting.
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Old 12-05-2009, 12:59 PM   #24
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I'll be darned. I looked in my '83-'86 service manual and it isn't shown there either. Went out to the garage and looked at the engine and sure enough, there's a phenolic spacer there. Mine's an '84.
My memory is really starting to suck. I've had that engine apart and don't even remember that spacer.
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Old 12-05-2009, 03:44 PM   #25
Ghost_Mutant
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Quote:
Originally Posted by brucifer
I'll be darned. I looked in my '83-'86 service manual and it isn't shown there either. Went out to the garage and looked at the engine and sure enough, there's a phenolic spacer there. Mine's an '84.
My memory is really starting to suck. I've had that engine apart and don't even remember that spacer.
I got into the attic and retrieved two carb insulators and two heat insulators.

First photo shows the 83 carb insulator/manifold attached to the carbs from my 83 XR500 restoration. Next to it on the right is the 85 or 86 XR600 carb insulator with the machined cross port I bought off ebay. Below both are the respective phenolic heat insulators that are a little bit different. One side of the heat insulator is machined for O rings, this side seals to the head.




Here is a closer view:


The XR600 carb insulator has the MG3 printed on the upper side as shown in the previous photo of this thread. I think the 85 XL600s also have this style of carb insulator, and I now think that the brown phenolic heat insulator was part of the package.

The 84 carb insulator looks like this one with the machined cross port. What's weird about the 84s is that the heads also have the reed valve installed. Honda apparently had both for the 84 model year (at least for the XR500). This is also a mistake in the manual, since it says that 84s don't have the reed valve. I have two 84 XR500 heads and both came with reed valves.

I'll try to be careful not to break my heat insulators since you can't get them from Honda anymore. They do appear to be brittle and somewhat fragile.

I'll stop here before I get accused of hijacking the thread
Hopefully one of the 85 XL600 owners can take a photo of the top of their head where the reed valve would have been. I'd like to see how things changed from the 83/84.
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Old 12-05-2009, 09:23 PM   #26
jdlcruiser
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Spacer

I pulled my 86 apart tonight and it more resembles the XR in the previous post. Unobtainable o-ring and spacer. Not where I can take a photo of it at the moment.

BTW Love the 700S. THat was my first street bike. Especially sitting next to the XL which is what I am working on now. Firefighters and their free time, cant tell you how much rusty old crap I have worked on off the back of a pumper. Well done.
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Old 12-06-2009, 06:45 AM   #27
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Honda had some problems with the release of the 1983 model XL600. It was related to stalling. The remedy was a kit that include a new intake manifold and a CDI with a different ignition curve. I actually saw one of these kits on ebay a while back and had no idea what it was for at the time. That homemade intake plate probably fixes that particuliar problem of the '83's. I would reuse it.
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Old 12-13-2009, 07:23 AM   #28
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Wow, cool info Clayjars. Thanks. I had never heard of that.
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Old 12-21-2009, 11:38 AM   #29
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You can always pm ZombieStomp.
He is the guru of the Xl/Xr Hondas.

The stator is definately the weak spot on the hard-to-start 600's
Change it and it'll be a 3rd kick start everytime.
Good luck
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Old 12-21-2009, 05:25 PM   #30
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