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XRs only Mikuni Flatslide Carb

By DSTerry,
in XR600R & XR650R/L

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DSTerry

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I'm looking at this carb for my 89 XR600.

http://www.xrsonly.com/content/index.php?page=shop.product_details&flypage=shop.flypage&product_id=549&category_id=423&option=com_virtuemart&Itemid=70

For about $250, seems like a pretty good deal. It comes with a new cable, throttle, and air box adapter. Just started shopping around to see what I can find.

Been reading a bunch of threads on carbs. A bit overwhelming! My bike is all stock except for the supertrap exhuast. Not really after a ton more performance. Just a good reliable carb that I won't have to worry about. Don't know how much better a pumper carb would be for my setup, or if I really need one for the extra money.

I read somewhere that this particular carb from XRs only does not come with a choke. Is this correct? (I did read a lot of threads so I may be mixing this up with another carb).

Any comments? Thanks.

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Grand Master

ballisticexchris

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that is the tm40 you need the pumper carb or it will not be any better than what you have my .02

I do not recommend the Mikuni flatside carb. The jets are not common, hard to come by and they are pretty difficult to tune.

Your best bet is to get a Keihin FCR41 kit from Sudco.

http://www.Sudco.com/CatalogJPG/023.jpg

Very easy to tune. Sudco will pre jet it for you so it's a bolt and go. I think it does cost a bit more than 250 bucks. I thought that Mikuni was around 450 bucks?

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Old Dog

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I do not recommend the Mikuni flatside carb. The jets are not common, hard to come by and they are pretty difficult to tune.

Your best bet is to get a Keihin FCR41 kit from Sudco.

http://www.Sudco.com/CatalogJPG/023.jpg

Very easy to tune. Sudco will pre jet it for you so it's a bolt and go. I think it does cost a bit more than 250 bucks. I thought that Mikuni was around 450 bucks?

+1 :moon:

I got my 41mm FCR from Sudco late last Summer, bolted it on and it was good to go. I had previously run two Eddy Pumpers that self destructed after a few months, and even when the Eddy carbs were working good they still weren't as good as the FCR. :cheers:

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DSTerry

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Wow, $562 for the FCR Keihin.

I don't want to end up with a crappy carb, but if the Mikuni is as good as stock, that may be just fine. My stock carb is completley worn out. See this thread:

https://www.thumpertalk.com/forum/showthread.php?t=858969

But if it does have problems or if I can't get parts for it, then it may not be a good idea.

Thanks

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Grand Master

ballisticexchris

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Wow, $562 for the FCR Keihin.

I don't want to end up with a crappy carb, but if the Mikuni is as good as stock, that may be just fine. My stock carb is completley worn out. See this thread:

https://www.thumpertalk.com/forum/showthread.php?t=858969

But if it does have problems or if I can't get parts for it, then it may not be a good idea.

Thanks

Where did you come up with that price?

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Grand Master

Horri

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Can't say I've ever had any trouble getting jets for my Flatslide Mikuni ..even though it must be easily a good 20 years old by the look of it. It's a b.......r to tune but I believe the new models are pretty easy to work on..None of that weirdness on the top of them like the old models have for adjusting idle etc,,just a simple screw system like Roundslides.Your call though. Personally I'd be buying any Flatslide/Roundslide of whatever size is needed from any bike..Two Stroke/Four stroke and rejetting it to suit..Just like we always did in the old days..$100.00 secondhand is all I'd pay for a carb but I'm a tightwad. Changing needles or adjusting the needle in the older models is also a bit of a pain ,hopefully the newer ones would be slightly better designed in that dept as well..Course I wouldn't expect you to buy used as you may end up with just another bung carb like your other two..Always the risk with used carbs. Guess it boils down to ,,Can you be bothered with the hassle of setting up a Mikuni..or shall I just buy a Sudco thats ready to go off the shelf..Myself I just find it hard to justify $500 odd dollars for a carb..

Edited by Horri
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DSTerry

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Not to worried about the tuning. Changing needles, jets, pilots, no problem. Used to tune my 125 2-strokes carbs from track to track. Had an assortment of parts for every condition.

I to would rather buy a used carb and save some money, but don't want to end up with the same thing I have now.

On the XRs only website, they say the Mikuni carb comes with an assortment of jets for fine tuning. Plus they put in what they think you will need right off the bat. But who knows how accurate it will be. All I really want is a carb that will get rid of my awful idling problems. I want it to run good too and be reliable.

When I was racing 2 strokes back in the day I was very picky and my bikes were tuned to perfection. On my 20 year old thumper, I just want something reliable. If it doesn't snap off the bottom like a race bike, no big deal. Still want it to perform well though.

Thanks.

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Grand Master

Horri

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Yeah I'm not sure what jets that Flatslide Mikunis running in the XL500..Pretty sure it's a 38mm so whatever it's running may not apply if you get a 41mm..It's been a while since I had it apart. If you do happen to buy the Flatslide I can pull it off and have a look if you like..That'd give you a rough benchmark to work from .Hopefully someone else with a Flatslide on a 600 will pop in with advice..Anyway..Let us know what you go with and if you need any help..and as I said the older Flatslides are a dog to work on,,I'm sure the engineering has improved over the years so the one you get won't be as bad as that one of mine.

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Grand Master

ballisticexchris

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Not to worried about the tuning. Changing needles, jets, pilots, no problem. Used to tune my 125 2-strokes carbs from track to track. Had an assortment of parts for every condition.

I to would rather buy a used carb and save some money, but don't want to end up with the same thing I have now.

On the XRs only website, they say the Mikuni carb comes with an assortment of jets for fine tuning. Plus they put in what they think you will need right off the bat. But who knows how accurate it will be. All I really want is a carb that will get rid of my awful idling problems. I want it to run good too and be reliable.

When I was racing 2 strokes back in the day I was very picky and my bikes were tuned to perfection. On my 20 year old thumper, I just want something reliable. If it doesn't snap off the bottom like a race bike, no big deal. Still want it to perform well though.

Thanks.

Before you go out and buy a carb. Have you double checked the pilot to make sure it's not clogged?

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DSTerry

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I would love to spend under $200 to get my problem fixed. Ya the bike is not worth much, though I plan on keeping it for a while.

It has been rebuilt from the ground up with all the suspension and rear disc from a '93. Plus I was able to get dual registration for it. It has all the lights, 200A stator, small speedo and key switch on some custom machined parts I made. Plus a NiMH battery pack and bracket I made for under the seat.

Anyway, my point is I don't mind spending a little bit of money on it.

When I rebuilt both of the carbs, I spray carb cleaner through all the orfices and make sure it squirts out the other end where it is suppose to. Then I run compressed air to blow everything out. The pilot jet was also prefectly clean.

The problem I am having with the carb is that when I slowly open the throttle and release, it gets stuck in a high idle state (even with the throttle stop all the way against the idle screw). But then I give it 1 or 2 blips and the idles comes back down. When stuck in the high idle state I can also bang on the side of the carb with a screwdrvier which brings the idle back down. In a previous thread we pretty much determined that the body of the carb may be warn out and the slide was getting stuck in there possibly due to the strong vacumme inside the carb. There are a few wear marks in the body where the slide lives.

But if anyone else has any other ideas before I spend money on a new carb I would like to hear them. Check out my other thread to see what I've already tried. Sounds like others have had similar problems and are looking for a way to possible fix this in the stock carbs.

https://www.thumpertalk.com/forum/showthread.php?t=858969

Thanks.

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bigredpig

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I do not recommend the Mikuni flatside carb. The jets are not common, hard to come by and they are pretty difficult to tune.

Your best bet is to get a Keihin FCR41 kit from Sudco.

http://www.Sudco.com/CatalogJPG/023.jpg

Very easy to tune. Sudco will pre jet it for you so it's a bolt and go. I think it does cost a bit more than 250 bucks. I thought that Mikuni was around 450 bucks?

:moon:

I have the hrs42 and the fcr41/40mm what ever and I have jetted both the hrs was so easy jets are harder to get but it was easy to get right there. I paid 200+100 for new cables

the fcr is a bitch to set up right! I have got it close but it is a bitch to start when hot and yes jets can be found but it have more jets to set up:banghead: fcr ebay 200+35 for cables

I like my hrs42 much better it was easy to set up and runs better.

if you would like I have my stock carb from my 88 xr600 you can have it! you pay for ship.

the tm40 for $250 at xrs I have that to. I will sell it for $90+ ship no cables for it. ever thing is there and it will need to be jetted.

my .02:p

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DSTerry

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Is this the right model XR650 carb. Looks like a good deal. No cables though.

http://cgi.ebay.com/ebaymotors/Honda-XL650R-XR650-XR-650-XL-Carb-Carburetor-99_W0QQcmdZViewItemQQhashZitem5d263df5bbQQitemZ400073553339QQptZMotorcyclesQ5fPartsQ5fAccessories

Do you need the entire throttle assembly with cables? Just curious what is different about the cables and/or throttle on the XR650 vs the XR600.

Thanks

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