Yamaha XT225

SoCal250 · April 05, 2024, 05:02:27 PM

I bought this '05 XT a while back in non-running condition and only 3100 miles from a local guy who said it wouldn't start again after it had been used during the previous fall riding season. Supposedly it was his girlfriend's bike. He didn't seem to be very mechanical and said he didn't want to deal with it, so he put it up for sale.
When I picked it up it was still dirty, he didn't even bother to wipe it off before showing it, and it was clear he hadn't done much recent maintenance on it. The oil was filthy, some spokes were loose, and all he had done to attempt to fix the no-spark issue was replace the plug.

xt225_purchase day_2022-03-17.jpg

After I got it, I cleaned it up, and replaced some missing hardware and a broken signal lens. Then I went through it, changed the oil and filter, rebuilt the carb, replaced a few electrical items, and determined the cause of the no-spark issue was a bad stator.

After replacing the bad part, I thought everything was done and I was going to be able to enjoy it. But it only ran for 15 miles and almost stranded me on the first test ride. I got tired of working on it so I pushed it to the back of the garage and moved on to other bikes projects since I have more than enough to keep me busy.

SoCal250 · April 05, 2024, 05:16:39 PM

After it had been sitting in my garage for quite a while I decided to pull it back out and see what had caused it to lose spark again. That's when I found out the new aftermarket stator had failed on the first ride due to a defect. The manufacturer sent a warranty replacement unit and I popped it in and the bike fired right up. So, that issues is finally resolved!

And since acquiring it I've installed a few upgrades...

DMO Specialties foot pegs:
xt225_peg upgrade_2022-04-19.jpg

Acerbis Rally Pro hand guards and MZS Tuning shorty levers, and I replaced the scratched up headlight cowl and front fender:
xt225_hand guards-levers_2024-02-28.jpg

This week I added a Precision Moto enduro rack:
XT225_PMR_Enduro rack_2024-04-02.jpg

XT225_PMR Enduro rack install_2024-04-02.jpg

SoCal250 · April 05, 2024, 05:36:09 PM

Although the ignition issue is resolved, it currently has a high-idle issue after it gets warmed up. Runs fine at start up and requires choke when cold. After the choke is turned off it has a perfect idle and performs as expected. But once it gets warm after about a mile the idle starts to hang and will not drop back to normal RPMs and then engine start getting really hot with the extra revs. I've done a quick check for possible air leaks with carb cleaner, but didn't find anything. Almost seems like a cracked intake boot and it only occurs when hot.

Took the carb off and went through it again and cleaned it in the ultrasonic. Also checked the cut-out valve cover that I had replaced because it was cracked when I picked up the bike, but it was OK.
xt225_carb disassemble_2024-03-18.jpg

However, after everything was back together...No change.

So, I have some more diagnostic work ahead of me to find the cause. It's practically unrideable now because it just revs out the whole time and starts to get super hot.

SoCal250 · April 05, 2024, 08:53:31 PM

almost forgot...
During my extensive electrical troubleshooting I discovered that the main switch had an intermittent short, one of the many issues that made finding the root cause of the no-spark problem so difficult.

Disassembled the switch, cleaned it up inside, checked the contacts, applied some dielectric, and it was functioning like new again.

busa1300 · April 05, 2024, 10:13:15 PM

That is a lot of various issues to try and find...no wonder the previous owner gave up on it. Hope you get to ride it soon

m in sc · April 06, 2024, 07:37:42 AM

might be the carb diaphragm. I looked at those before i bought my xr150, neat bikes for sure. you'll get it sorted.

85RZwade · April 06, 2024, 11:51:43 AM

You probably checked the valve clearances, but I don't see it in your process above. I'd include it in your diagnostic attack

SoCal250 · April 06, 2024, 01:03:39 PM

Quote from: m in sc on April 06, 2024, 07:37:42 AMmight be the carb diaphragm.

I checked the diaphragm really carefully and didn't see anything wrong with it. I can get a new genuine Mikuni one for about $75 (Yamaha wants $160), maybe I'll just fire the parts cannon at it. If it doesn't fix it I'll have a spare for my XT parts bin.

Quote from: 85RZwade on April 06, 2024, 11:51:43 AMYou probably checked the valve clearances, but I don't see it in your process above. I'd include it in your diagnostic attack

I have not checked yet but I did source the tools and gaskets in anticipation of doing it. Could a bad valve clearance cause a high idle like I have?

m in sc · April 06, 2024, 05:48:31 PM

id say probably not, a compression check would be easy to do though. that would show one hanging up

RustyRD · April 16, 2024, 09:41:01 PM

I know this is a way different bike than the kz1100 I had very similar condition, carbs are mikuni BS34 diaphragm slide, ran well but would not settle into a normal idle.. the situation I had was a combo of leaking rubber carb mount and low speed mixture adjustment. Took quiet a few try's to correct. Lean mixture in the low speed circuit seems to be the culprit.

SoCal250 · April 17, 2024, 12:31:07 AM

My carb is currently all stock with brand new genuine Mikuni jets. Below are the factory specs and what I've changed. Because these bikes are notorious for being on the lean side from the factory, it's a pretty common mod to increase the pilot one size. So, I'll be installing a #42.5 to see if that helps at all but I kind of doubt it. And on advice from another long time XT owner, the fuel screw has been changed from 2 turns out to 3, but no effect on performance or the idle issue.

2001-07 Yamaha XT225, Mikuni BST34 specs -- stock:
Main jet: #125
Pilot jet: #40 (to be increased to #42.5)
Pilot air jet 1: #70
Pilot screw: 2 turns out (increased to 3 turns out)
Needle jet: 0-1
Needle: 5DL27-1
Valve seat: 2.0
Float level: 14.1-15.1 mm (14.7mm)

A new diaphragm slide is on the way so I can see if that improves anything. I will be also be leak testing the rubber carb joint again to see if I can find any air leaks. Unlike the joints on RDs the XT part uses an O-ring between the cylinder, so I have one of those on order as well.

m in sc · April 17, 2024, 08:55:25 AM

.... do those have that plastic housing that runs up the side of the carb body? can't see it on the pic. they are NOTORIOUS for warping and leaking air. would be on the opposite side of the cable wheel. there was a TTR225 i worked on years ago that had one that would leak like just enough to completely fuck the idle and transition circuit. IF i remember correctly, has an o-ring at either end and it screws to the side of the carb body.

SoCal250 · April 17, 2024, 11:31:57 AM

Quote from: m in sc on April 17, 2024, 08:55:25 AM.... do those have that plastic housing that runs up the side of the carb body? can't see it on the pic. they are NOTORIOUS for warping and leaking air. would be on the opposite side of the cable wheel. there was a TTR225 i worked on years ago that had one that would leak like just enough to completely fuck the idle and transition circuit. IF i remember correctly, has an o-ring at either end and it screws to the side of the carb body.

Yes, it has the air cut-off valve on the side. The TTR225 and XT225 share a lot of parts including the carb. The cut-off cover was replaced with a brand new one because it had a crack in it. (The O-ring, diaphragm, and spring were reused.)

When I was installing it, I was thinking that it would be an easy spot to develop a leak because of the design. Who knows, maybe I got a cover that doesn't fit well?
I'm planning a trip to Sudco to get some Mikuni parts, so I'll just add that O-ring to the list.
And when I get the bike out to do my leak testing I'll check that cover too.

News:

Yamaha XT225