1984 xr250 r carby change

[the stig]

          I have a xr250 r with the twin carby's on it has any one on the Forum fitted a Single carb on One.
          if so could you tell me what  later model Honda parts fit
          Also are there any gains  or losses as far as starting goes. and running goes.

          Thanks  The Stig
         

[Trokel510]

Hi Stig

I can't help with any advice as far as changing to the single carb but instead was just curious as to why you would want to change it. I have heard many people say that the twin carb models are a pain in the behind but personally i have not had any problems with mine. I have an 83 built 84' model XR250R and an 85' XL250R both with the original twin carbs and of all the bikes i own (which is a few) they are the only ones that i have not touched the carbs on and personally i reckon they go better than the single carb models. At the very least they feel to have a more defined rush of power when the second one opens up. If you are having problems with starting etc. then I think that you would be better off trying to get to the bottom of the problem first with the original setup rather than trying to change it as you may well introduce more problems but that is just my opinion. I think if you were to explain what the issue is then I am sure that some of the knowledgeable people on here will be able to offer some good advice on how to fix it.
Anyway all the best with it they are a great little bike. 
Cheers Troy

[mick25]

Hi Stig

I can't help with any advice as far as changing to the single carb but instead was just curious as to why you would want to change it. I have heard many people say that the twin carb models are a pain in the behind but personally i have not had any problems with mine. I have an 83 built 84' model XR250R and an 85' XL250R both with the original twin carbs and of all the bikes i own (which is a few) they are the only ones that i have not touched the carbs on and personally i reckon they go better than the single carb models. At the very least they feel to have a more defined rush of power when the second one opens up. If you are having problems with starting etc. then I think that you would be better off trying to get to the bottom of the problem first with the original setup rather than trying to change it as you may well introduce more problems but that is just my opinion. I think if you were to explain what the issue is then I am sure that some of the knowledgeable people on here will be able to offer some good advice on how to fix it.
Anyway all the best with it they are a great little bike. 
Cheers Troy






I have to agree with Troy i would keep the twin sett up
I had a xr500 84 for a while they have the twin carb sett up , once they are jetted and sinkarised right
 they work great .

[Trokel510]

I have to agree with Troy i would keep the twin sett up
I had a xr500 84 for a while they have the twin carb sett up , once they are jetted and sinkarised right
 they work great .

Hi Mick

I am looking at buying an 84XR500 in the next day or so - Any advice or things to look out for.

Cheers Troy

[mick25]

The Xrs have the spark plug between the two exhaust valves and there's not much meat there and can crack there , but saying this mine was fine , the 350 and 250 had head cracking probs two they don't have much fin length on there heads that's why ballards done the welded on longer fin heads mods to cool them better .

A mate of mine got a guy in Sydney that puts a insert in the head to fit a smaller dia spark plug to make a bigger gap between the exhaust valves to stop cracking heads.
But the xr500 83 ,84 go well

[Trokel510]

The Xrs have the spark plug between the two exhaust valves and there's not much meat there and can crack there , but saying this mine was fine , the 350 and 250 had head cracking probs two they don't have much fin length on there heads that's why ballards done the welded on longer fin heads mods to cool them better .

A mate of mine got a guy in Sydney that puts a insert in the head to fit a smaller dia spark plug to make a bigger gap between the exhaust valves to stop cracking heads.
But the xr500 83 ,84 go well

interesting
I have heard about this problem a bit lately in discussions i have had with other people regarding these models but am yet to experience it myself. From what i have found most bike models both old and new seem to suffer from some sort of unique problem but I like to think that if a bike as old as these is still going OK then maybe the problem wasn't as bad as it was made out to be. Fingers crossed.
Anyway Thanks for the info.

[the stig]

        Not really having a lot of trouble with it it is sooting up the plug .
        The motor has the big fins on the head and it has had the plug hole welded and a smaller
        plug fitted.
        It had a Chatter come rattle in the top end so I replaced the timing chain cam bearings and
        a New chain tensioner and I still got the rattle not all the time.
        Read in a magazine that when the Piston in the secondary carby wears that can cause them to
        rattle at certain throtle  positions..
        So I thought I would ask the question as Honda only had this se tup for a few years  then went
        to a single Carby.. If I have to spend money I would go that way.
        I am not worried power losses or Gains
       

       Thanks  The Stig

[FourstrokeForever]

I think XR's Only still make an adaptor manifold to fit a single carb onto the twin carb head. I know they used to.

Other than that option or making one yourself, maybe a later model single carb head will fit the original barrel etc.?

Back in the day, we used to adjust the cam that works the carbs so that the first carb stayed solo for longer and that takes about 2 minutes to do. Check out the mechanism and close the gap on the striker for the second carb. With the increased time between the first and second carb opening, the XR's run much cleaner off the bottom and are heaps easier to start after a stall or stack.

Hope this helps.

[the stig]

       Thanks FsF that was good to know  I have been told that the manifold and boots from the 76  to 78 xr
        fit this model.
        but will look at the Cam adjustment as well .
       
        Thanks The Stig
       
     
       

[FourstrokeForever]

There is no way the inlet manifold from an XL (there was no 76-78 XR) will fit the twin carb head Stig. Someone has fed you a load of BS

[the stig]

There is no way the inlet manifold from an XL (there was no 76-78 XR) will fit the twin carb head Stig. Someone has fed you a load of BS

     Sorry f s f my typo mistake it should have read 86 ton 87 will fit
    The stig