Need help to sort this Piggie out!

Hi Lads!

I can see it's been a long time since someone asked you wizards for jetting help, so I thought I'd jump in!  

I bought an XR650R ('03, 12,000km) 1.5 years ago. It's been running rather terribly ever since, except for a hadful of rides, where it's really purred and felt damn good. These rides have puzzled me a great deal, of course, and now I wonder why it doesn't run like that every day. It has a hard jerk, when easing off the throttle and then slowly picking it up. A bit uncomforbale without a bit of clutch. Changing lower gears is usually jerky too. In general, it's very hard to ride smooth, without fiddling with the clutch a lot. I forgot the gearing, which is not stock, Will post later if needed.

I live in north Vietnam, and the weather here varies from 10-12 degrees (50F) in the winter, to 40+ (100+F) in the summer, and of course monsoon rain. The variable I intend to ask you about is the humidity, which can get close to 100% at times. We're talking windows that are foggy on the outside.

The previous owner told me I should NOT to mess with the jetting, as he had been through the combinations and found the far best setting. I know he knows a lot about bikes, and I know he spent a lot of time on the bike, so I didn't, but surely there's room for improvement.

The bike is uncorked, and set up like this:

- IMS 4.6 gallon tank
- standard carb, new throttle valve and has been rebuilt with a kit recently.
- standard header/exhaust, with a HRC tip (I think?)
- new rubber between carb and cylinder
- UNI foam filter (no holes in cover)
- 170 main
- 68s slow
and here's the odd parts:
- clip on 4th from the top down
- a B53F needle (is 'F' the original needle??) I'm not sure what the difference between the E and F are?

The pilot screw is about 2 and 1/6 turn out. I checked the plug, but without any hard run / high revs prior to checking. Look ok to me:



I tried to change the clip to 3rd position, and right after the bike ran super sweet, and I thought I had solved the problem, but a few days later, it was worse than ever, and I was told it made grey/white clouds when accelerating hard. It was lacking power, both low and high, and it was vibrating a lot too.

I've adjusted the valves twice within this month, second time to verify, so they should be ok. What condition they are in, I have no idea! https://www.youtube.com/watch?v=Tyboh7UAuRw

In general, would I need to change the jetting specifically for summer and winter? Or will a good setting handle both? I'm mostly riding around sealevel (12m) but I do ride in mountains also, less than 7000 feet.

If you could help me with a base setup, or comment on the current one, I would be very happy. Although it does look like I will be needing the 'E' needle to follow the charts?

You seem to have 2 issues carb which looking at plug is running lean and the clutch which is playing up, the clip position won't make much difference to running as I understand it all this does is provide an idle mixture tuned by the mixture screw ?....as regards your clutch you really need to find out what's goign on in there are stock clutches are normally very good and trouble free.

Mauser wrote:You seem to have 2 issues carb which looking at plug is running lean and the clutch which is playing up, the clip position won't make much difference to running as I understand it all this does is provide an idle mixture tuned by the mixture screw ?....as regards your clutch you really need to find out what's goign on in there are stock clutches are normally very good and trouble free.

Thanks, Mauser! You really think it looks lean? This was taken before I changed from 4th to 3rd clip. The clutch is fine ... why do you think it has a problem?

Hi you mentioned this..."Changing lower gears is usually jerky too"...yes I think it looks lean to me ? have a look here and see what you think ?
http://www.max-boost.co.uk/max-boost/internet_articles/Spark%20Plug%20Reading.htm

Mauser wrote:Hi you mentioned this..."Changing lower gears is usually jerky too"...yes I think it looks lean to me ? have a look here and see what you think ?
http://www.max-boost.co.uk/max-boost/internet_articles/Spark%20Plug%20Reading.htm

Yeah, you could be right! So what do you think I should do from here?

lean!, are you kidding, that plug is soaking in fuel ..., or the mtr is using oil, your needle clip position sets fueling over most of the usable range of riding i.e 1/8th-3/4 throttle opening. id say your needle is too high, 1st off try it in the middle clip position[ 3rd from top is std setting], that is as long as the bike's carb has been thoroughly cleaned, particularly the idle circuit air supply side, make sure your on the low side of the float setting spec[16mm]id set it at 17mm, try that and let us know if you need more help

temporary kiwi wrote:lean!, are you kidding, that plug is soaking in fuel ..., or the mtr is using oil, your needle clip position sets fueling over most of the usable range of riding  i.e 1/8th-3/4 throttle opening. id say your needle is too high, 1st off try it in the middle clip position[ 3rd from top is std setting], that is as long as the bike's carb has been thoroughly cleaned, particularly the idle circuit air supply side, make sure your on the low side of the float setting spec[16mm]id set it at 17mm, try that and let us know if you need more help

I tried the needle at 3rd position, after cleaning thoroughly, but it ran VERY lean! As in hot, shaky and smoking, and very little power. I changed the needle back to 4th, and it helped a lot (please note that I have the B53F needle) Should the main be larger than 170? Maybe a larger main, and then needle on 3rd clip? I read about people at the same altitude and temps as me, who run 175 or even larger ... I have a feeling the cam and valves are shot. It's been run low on oil on some very hot days Not sure what this means for the jetting?

temporary kiwi wrote:lean!, are you kidding, that plug is soaking in fuel ..., or the mtr is using oil, your needle clip position sets fueling over most of the usable range of riding  i.e 1/8th-3/4 throttle opening. id say your needle is too high, 1st off try it in the middle clip position[ 3rd from top is std setting], that is as long as the bike's carb has been thoroughly cleaned, particularly the idle circuit air supply side, make sure your on the low side of the float setting spec[16mm]id set it at 17mm, try that and let us know if you need more help

Must be my eyes I cannot see it soaked in fuel ?.....even with glasses on   
Anyway here is another article which might help....
http://www.iwt.com.au/mikunicarb.htm

LOL "It's been run low on oil on some very hot days Sad Not sure what this means for the jetting?"

For the jetting it means the same as for the handlebars..... it's shot - that is, if you mean with 'low on oil' too little oil.
Take the rocket cover off. If you see marks on the cam followers then take the lot off, and fix what you'll find.
Only then jet it to perfection, but trying to do this now is kidding yourself.

Its nearly impossible to tell  what the problem is without seing the bike but going by what you have said and shoved here it could be dirty carburettor or some damage to the top end from running low on oil , you need to take it apart and inspect it , measure the compression if you can or pull out and check the piston too , even if everything is within the spec  you will have the piece of mind that you know what is the condition of the engine inside .

Madder,

here's a quick test: start your bike with insufficient oil and ride it around the block!
Quick hmm?
Not cheap though, and by the time you'll come back - that is, if you do! - your "jetting will be out".


Open it up as I told you bru, it will quickly and cheaply (no gasket required) tell you what is wrong!