Yamaha XT225

[SoCal250]

Not fixed after all.
Took it for a longer ride today and the revs still hang around 2-3K sometimes. Also noticed when shifting that it would over-rev each time the clutch is pulled (despite letting off throttle). The problem isn't as bad as it was before and it's not constant. I did 30 miles and it started about 4-5 miles in. The issue was tolerable, but annoying.

At least I was able to get in the longest ride I have done on the bike since I bought it.  So I have that going for me.

[RattlecanResto]

Ha, I had a TTR225 and had similar issues. Electrical leave you stranded issue ended up being bad/stuck contacts in kill switch. Carb worked fine after cleaning but was only good to sit for a week or so with pump gas cuz it was so finicky. I def would have eventually replaced carb if I had kept it. Loved it when it was running tho

[RDnuTZ]

any chance your throttle cable is routed too close to head or exhaust pipe at some point? Or possibly the throttle inner wire isn't sliding freely inside outer sheath from age/use?

[SoCal250]

any chance your throttle cable is routed too close to head or exhaust pipe at some point? Or possibly the throttle inner wire isn't sliding freely inside outer sheath from age/use?

No, it isn't throttle cable related. It has a push-pull dual cable setup and the pulley on the side of the carb is returning all the way to the closed position at the stop while the issue is happening.

[m in sc]

maybe a new diaphragm/slide spring is due.   

[SoCal250]

maybe a new diaphragm/slide spring is due. 

Possibly, I'll get one and throw it in there and see what happens. Worth a try at this point.

Also, next time I have the carb out I'm going to carefully look at the slide guide. Maybe it's binding up when getting hot? New ones are available from Mikuni for the BST34.

[SoCal250]

maybe a new diaphragm/slide spring is due. 

Possibly, I'll get one and throw it in there and see what happens. Worth a try at this point.

Ordered. But as seems to be the case with my luck and obtaining parts, there is a 4-week back order on the spring. 

[m in sc]

doh.
in the meantime can you add some preload to it? for a test? like 1/4" or so.

?

[SoCal250]

I have some other parts I'll need to install soon so I may see what can be done with the OE spring while I'm waiting for it. It's a pain to take the carb out of that bike but it looks like I'm going to have to do it at least twice now.

[SoCal250]

Got some parts from Moto Lab in Iowa (https://www.moto-lab.com/). A great source for Mikuni BST carb parts! Thanks so-cal-sdr200 for the recommendation! 
I ordered stuff midday on a Monday and it was at my door Wednesday. Unlike some other places, everything he has on his site is in stock.

Pulled the carb today and made some changes:
 -Increased the pilot from #40 to #42.5
 -Shimmed the needle
 -Installed an extended pilot fuel screw set. Now I won't have to pull the carb to make adjustments.
 -Installed the missing rubber boot on the choke cable fastener on the carb.
 (Left the main at the stock #125 and kept the fuel screw at 3 turns out.)



Inspected the slide guide and it's in good shape and shows no evidence of binding or sticking. I polished the slide edges with some fine emery cloth since the brand new part had a little bit of flashing and rough edges, and lubed the blade channels with some 2T. I have a new BST34 guide but decided against replacing it because it wasn't necessary (and I don't have the correct Torx tamper bit for the screws).
And I didn't replace the slide spring because the part is still 3 weeks out on backorder.
The first 2 items are part of a kit from ProCycle and recommended upgrades to improve performance on the XT.

No test ride yet, but maybe tomorrow if I have time.

[m in sc]

nice. hope that cures it.

fuckin' 4 strokes...   

curious to see how it works out. good job in the extended screw. i have a 60? degree angle bit driver just for that same issue.

[SoCal250]

Attempted a test ride today but didn't even make it out of the driveway. It's worse!

Fired it up and as soon as I could turn off the choke the idle started rising. Checked the cable pulley on the carb and it was still sitting on the stop screw. Blipped the throttle a few times and no change, still hanging. Shut it off and restarted and the idle was normal again. Then it started hanging again.
I also noticed a new noise that sounds like a pulsing air/vacuum leak (kind of like tsstt-tsstt-tsstt-tsstt). It's from somewhere on the rear half of the engine but couldn't pinpoint it. It's a little difficult to hear over the exhaust noise. I sprayed carb cleaner in a few places looking for a leak and found nothing.
When blipping the throttle it now has a bad blubbering stumble that it didn't have before, but I couldn't mess with the fuel screw because it was too hot to get a hand in there, so I just put it away to deal with later. Too hot and pissed off to tinker with it any more today.

And I had to get the MB5 ready for the show tomorrow anyway.

[SoCal250]

This bike got me so frustrated that I stuffed it in the back of garage since I have too many other projects to work on. Well, after a year I decided it was time to pull it out and get back at it to see if I could resolve the issues and get it running correctly.

This thing has been so troublesome since I brought it home that it has earned the nickname of "the POS". The first year or so was spent playing whack-a-mole with various electrical issues, some of which left me stranded on the side of the road on the first few test rides. In the first 2-1/2 years I was only able to put 67 miles on it.

Over the Labor Day weekend I went through the carb again, replacing a leaking float valve and installing all new jets. The cut-off valve diaphragm and the three associated O-rings were also replaced. I also raised the float 0.75mm. After some road testing and fine tuning the jetting is now: #130 MJ, #42.5 PJ, needle shim. 3.25 turns out on the fuel screw. (Stock is #125, #40, 2 turns out.)
During my ownership, every single part of the carburetor has now been replaced except for the body, the cap, and the bowl!


In an attempt to fix the hanging idle issue I replaced the carb manifold and O-ring. In the past I wasn't able to find any air leaks there but it sure looked suspect. It was crusty and less pliable than the new one.

[SoCal250]

So... after the latest wrenching attack, the POS is running perfectly now! In the first few days of the month I've done over 160 miles, including 81 yesterday. Friday's ride was more miles than I was able to put on the bike in the entire first 3 years I've owned it!



Sep 03 ride: 60 miles through Long Beach and the terminal area:




Sep 05 ride: 81 miles south on PCH to Dana Point
Corona del Mar


Dana Point Harbor


The POS performed flawlessly. Fires right up, smooth idle, revs return to idle quickly after whacking the throttle, clean revs all the way to redline, and no hesitation. 
Now that it runs great and is reliable, I'm going to (as my friend Darryl always says) "Ride the piss out of it! 
A 1 tooth larger front sprocket is coming next week, and sometime soon I'll put on some more street-oriented tires since it won't see dirt much.

On to the next bike project...

[busa1300]

 
Glad you found some peace of mind with your project.
I know when I get pissed off and push stuff back for a while....I usually forget what exactly the issues were and have to start from the beginning again.