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I Need to know what kind of Carbs can go on a 95' LC4 620RXC

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In my past thread you might have read that I just bought a this bike and I have been having some problems with Hot Starts. The Carb that is on the bike is a Mikuni but unknown model. From what I can see there is no Hot Start or Warm Start button on the carb, and I am feeling like that might be a problem.

It is basically impossible for me to kick over this bike when it is hot. Could some one give me ideas to fix this or possible the make and models of carbs without this problem. Thanks

James

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James,

I'm not sure what type of carb you have installed on your bike, as I looked at a manual on-line for the 95 RXC and it showed Delltoro as the stock carb???????

Other than the hot starting problem how does the carb act???? Any dead spots or hiccups???

What's the plug look like??

Might want to try to try using the choke and see if it helps.

Also go to KTMtalk.com and post this in the LC4 section and you 'll get better info over there for the KTM's

Other than that if your looking to replace the whole unit you should be able to use just about any make of carb...seems everyone prefers the FCR39 or 41 carb or the BST40 carbs.

Good luck

Chris

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I have the Mikuni BST40 in my bike already. I was just curious because that carb does not have a Hot Start button. Is that because it does not need one due to improvements or is it just not the best carb for this bike?

I replaced the plugs on the weekend and I have yet to really go out for more than an hour and ride so I am not sure how it will hotstart yet. The old plug did not seem clogged or too dirty. There was some carbon build up around the threads and a usual amount of carbon around the tip but it was nothing too bad.

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The BST is not the worst carb to have.

My bike has the same carb and works fine.

Might need to be re-jetted some, but it should fire when hot.Try using the choke next time and see what happens.

I have to do this sometimes on my bike,Now that I mention it my manuals refer to the choke as the hot-start.

Worth a shot...

What areas do you ride at???

Noticed your a local.

Chris

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Evans Creek, Rieter Pit, and other local spots... Rode till I was like 17 and I am getting back into it now. I am located in Renton, WA.

Let me know if you want to hit some trails up.

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I've never tried the BST on a 620, but it is a very easy carb to start the bike with hot or cold. The LC4 seems to be fairly sensitive to the idle mixture. A half turn one way or the other off of ideal can make it tough. Anyway, the RXC airbox is *MUCH* better than the later e-start LC4's (where I suspect that BST came from ??). You may want to check the jetting in it. It should have the needle clip in the middle position (#3), a 47.5 idle jet, and somewhere around a 160 main. About 2 - 2.5 turns out on the fuel screw should be close. While you're in there, check the float level, as they are usually not right. That combination should get you in the ballpark to where the bike will be happiest, and at least make the bike start fairly easily. I have modified BST's on both of my 640 Adventures, and they are very easy to kick over and start.

Also, for some reason, I have found that at least *MY* '96 620 RXC likes a fresh plug fairly often, and it didn't matter what I used. So now I use a cheap NGK D8EA and replace them whenever I feel like it.

Now, the older Edelbrock carbs were horrible on this bike, and that's what KTM saw fit to installing on my bike. I gave up on it and sold it long ago. I have no experience with the new Edelbrocks on the LC4, but they do work great on the XR650R. My 620 RXC has a 41mm FCR on it now, and I have found that it is easy to start, hot or cold, if I adhere to the start ritual.

Good Luck!

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I agree w/ Gaspipe. I had a modified E-Brock on my '98 RXC620 that ran and started "OK" but I knew I could do better. I bought a used BST40 and it starts VERY easily, kick or button and runs real well. I jetted it w/ info from advrider.com and was close enough on the first shot to leave it alone. The BST is a good low buck carb too. I also have a '98 RXCe400 that has the modified E-Brock on it and it starts and runs fine. Go figure. Get a BST, and from a carb standpoint, your problems will be solved.

-Terry

'98 RXCe400

'98 RXCe620

'89 FXR-1340

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I have the Mikuni BST40 in my bike already. I was just curious because that carb does not have a Hot Start button. Is that because it does not need one due to improvements or is it just not the best carb for this bike?

I replaced the plugs on the weekend and I have yet to really go out for more than an hour and ride so I am not sure how it will hotstart yet. The old plug did not seem clogged or too dirty. There was some carbon build up around the threads and a usual amount of carbon around the tip but it was nothing too bad.

The BST 40 is a great carb and can be bought cheap on ebay. Most people that sell them are upgrading to the FCR carb. The BST is more fuel efficient and with a few mods can work well. The mods include drilling out the vacuum ports and shortening the diaphram lift spring.

http://www.motorally.ca/English/OnTheWeb/BST%20Jetting%20Guide.pdf

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