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1995 XR600R Project

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Hey guys, new to thumperTalk and just picked up a 1995 XR600R on a trade.

 

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Previous owner claimed that the bike would run, but we spent an hour kicking it over and over and we weren't able to get it running. Had a buddy that was able to kick it over and it ran for about 30 seconds before it died. While we had it running we would give it gas and it would fall on its face almost like there was a clogged jet. Went to take the carbs off to clean them and noticed that someone had drilled a giant hole in the side of the carb by the intake to the engine. There was a piece of electrical tape covering it, but i think the original intention was to have a breather hose run to that spot. Here are a few pictures of what I am talking about.

 

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Does anyone know why they would have drilled this hole in the side of the carb?

 

I have been able to get the bike to run one other time, but still only for about 15 seconds before it dies. I have cleaned the carb, adjusted the valves, tested wiring (ordered a new coil) and everything seems like it's within spec. I plan to pull the valve cover and possibly the head to inspect for any damage. I did notice that part of the choke plate is missing and am hoping it wasnt sucked into the engine

 

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I look forward to getting this bike up and running and I have some cool plans for this bike IF I am able to get it running without dumping a ton of money into it. 

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You do know where that missing part of the choke plate went, don't you???

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You do know where that missing part of the choke plate went, don't you???

Yup...pretty sure it's in the engine. My only hope is that someone before had this issue and tore into the engine to fix it. There are a few new gaskets that I can see on the engine. Hopefully that's the case but we will find out tonight when I pull the valve cover and possibly the head depending on what I see

 

Sweet graphics. :thumbsup:

Thanks!  B)

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I am planning on replacing the carb that came on the bike since someone drilled a giant hole in the side of the carb. I have been doing research on the FCR MX carb swap that a lot of people have done to their XR's. I haven't found much information about using a smaller FCR carbs (37, 38, 39mm) on these bikes. Has anyone tried this? I have found a few cheap ones on ebay and am wondering if it is a viable option, or if I should just wait to get a 40mm version that I know will work?

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The Honda CRF450's use the 40mm carb with the one exception of the 2008 which is a 41mm. The CRF250's and CRF450X use the smaller sizes FCR's.

Edited by mcma111
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Does anyone know why they would have drilled this hole in the side of the carb?

 

Being a crackhead is my first guess. And my second....and third.....and fourth...I'm also wondering what that epoxy-covered plate next to it is all about.

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I knew that looked familiar. Must have worked like a ''boost bottle''.

Yes exactly!

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Now I know, but that makes it even more horrifying. Butcher the carburetor for a mod that works on 0% of four strokes and 1% of two-strokes....

 

Anyway, I think a 38-40mm pumper will work fine as a replacement, although something larger would still work well and provide some room for growth. I had planned on using a 46mm Mikuni before cars and work got in the way of my 600.

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I figured there had to be some reasonable explanation for why someone would drill that large of a hole in the carb. When I got the bike there was a piece of electrical tape covering the hole. As soon as we got it to start the first time it did all it could to try to suck that piece of tape into the engine before it died. It looks like someone might have had it set-up properly with this mod before, but currently it is missing the metal tube that connects to the carb. It also has all of the stock pieces for the intake, not sure if those were supposed to be swapped out too...

 

Anyways, spent the last couple of nights taking the engine out to tear into it to see if there was any damage done by the piece of the choke plate that was missing. I could see that there were new gaskets in the engine before I pulled it and had hoped that someone had already taken the time to tear it down and rebuild it...and I was right!

 

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Removed the valve cover to check to see if the timing was correct and it looked pretty close, maybe a tooth off but hard to tell if you could get it to sit even.

 

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Everything looked really clean, and i didn't find any evidence of the choke plate. Decided to dig a little further since I was this far in.

 

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It looks like someone was in here recently, or they never really got the bike to run after the rebuild. There was very little carbon build up and a little wipe with the carb cleaner and everything looked clean again. One of the valves has a little damage on it and I am assuming that was from the choke plate. It looks like the valve is seating properly but I'm not sure if I should still replace it or not.

 

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I also found a pretty good deal on a 40mm FCR-MX on ebay that should be here this week. Hoping to get that mounted up and try to get the bike to run for more than 30 seconds before it dies. 

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Did you pour some kind of solvent like mineral spirits in upside down head to check for valve leakage?

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A piece of aluminum from the choke plate wouldn't be hard enough to beat up that exhaust valve like that. A wild guess says the piece stuck the exhaust valve open and the piston bent it. Then a BOOB with a hammer beat the valve head straight again. I'd replace that one valve , rather than have the head come off.

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A piece of aluminum from the choke plate wouldn't be hard enough to beat up that exhaust valve like that. A wild guess says the piece stuck the exhaust valve open and the piston bent it. Then a BOOB with a hammer beat the valve head straight again. I'd replace that one valve , rather than have the head come off.

I was kinda thinking the same, but the marks are in strange places on valve, like center, & the marks have weird shapes, like it was beaten with ??? beaver teeth or center punch or ??? If you have the money, & since it is apart, replacing the valve makes sense.

Edited by bork

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It looks like the divots are in carbon deposits on the valve like someone tried to chip them off. It's probably fine, but are you going to feel fine saving $50 on new valves if one of those cuts loose and takes the engine out? I hate replacing good parts, but some times it just isn't worth the risk of keeping unknowns.

 

It looks like the retainers, intake valves, and springs are all aftermarket.

 

The cam alignment is pretty typical for an RFVC that has ever been run longer than two seconds.

 

On the "boost bottle" mod again, they are of little to no value on most two-strokes and of zero to negative value on a thumper. Better off without it.

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The cam alignment is pretty typical for an RFVC that has ever been run longer than two seconds.

 

 

I run my cam 6* retarded  , with a good chain and sprockets , intentionally. I think that's also why my motor's never pinged with a 11.25 piston on 93 pump gas.

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