The XT550 Thread: Info, Stories and Mods Inside!

[xlv]

So how can i tell if i have a CDI problem or if it is just the carbs that makes the bike cut out in higher revs ? It has a new piston and reworked head with new valveseals so it´s in good shape otherwise.

/M

[motorcyclefanatic]

Originally Posted by xlv

So how can i tell if i have a CDI problem or if it is just the carbs that makes the bike cut out in higher revs ? It has a new piston and reworked head with new valveseals so it´s in good shape otherwise.

/M

I had the CDI fail on my XT once back in the 90's, wouldn't run at all. That's been my experience with other CDI failures over the years as well (GSF400 & VTR250 most recently). When they go the bike is dead.

[XTwarrior]

Originally Posted by motorcyclefanatic

I had the CDI fail on my XT once back in the 90's, wouldn't run at all. That's been my experience with other CDI failures over the years as well (GSF400 & VTR250 most recently). When they go the bike is dead.

This; when my stock CDI failed on me it cut out during a second gear pull and sputtered to a stop. It never started again until I got the hyperpak CDI.

If it is cutting out up top, I'd imagine a fueling issue (if it is drastically cutting off; IE sputtering until it comes back down).

[G600]

Originally Posted by xlv

So how can i tell if i have a CDI problem or if it is just the carbs that makes the bike cut out in higher revs ? It has a new piston and reworked head with new valveseals so it´s in good shape otherwise.

/M

Pfff... a problem like that can be a pain to figure out.

Is the bike new to you? Was it working right at some point or has it always acted like this?

Here is one thing to check if your bike is an ’82 model. When the xt550’s first came in ’82 they had a design flaw in the carbs. The fuel flow to the second (vacuum) carburetor was restricted. Under modest loads the engine would run normally, but at heavy throttle the second carburetor could run out of fuel.

Yamaha sold a kit to solve this problem. It is unlikely that this problem has not been solved in a 28 year old bike. If your XT is an ’82 that is. But then, I have seen stranger things.

[xlv]

Thank´s
The bike isn´t really new to me, i have owned it twice but i think it allways have had this problem exept i didn´t pay mutch attention to it earlier but now i feel like it has gotten worse, it´s an -83 modell. Guess i better tear into the carb,s and take a look.

/M

[vudu]

Hey XTwarrior,

"Question for you guys; Has anyone tried to go larger on the rear or the front tire?"

I recently replaced a 4.1 with a Trailwing 4.6 on the rear. Just clears the chain guard. Looks better proportioned. (horn!)

[vudu]

Hey xlv,
"So how can i tell if i have a CDI problem or if it is just the carbs that makes the bike cut out in higher revs"

You can do what i did and replace all the cheaper parts first. Regulator, coil, new battery. My symptom is a miss at idle resulting in a squeak when the plug doesn't fire. Goes fine at speed. I've ordered a Hyperpak. Patiently I wait.....

Previously I had the shop reset the float level and clean the carbs. $100 well spent.

[Zecatfish]

Originally Posted by vudu

Hey XTwarrior,

"Question for you guys; Has anyone tried to go larger on the rear or the front tire?"

I recently replaced a 4.1 with a Trailwing 4.6 on the rear. Just clears the chain guard. Looks better proportioned. (horn!)

My bike had a Cheng Shin 4.60x18 trials tire on it when I got it. I've ran a few old knobbies I had around from my two strokes. Wish I could remember the sizes of those.
Currently I'm running a 4.00x18 IRC TR-1 DOT Trials tire on the back. The front is still the same Cheng Shin Trials. I changed it out to a knobbie thrice and came back to the Trials tire. I just like the way they handle better than knobbies.

[XTwarrior]

Thanks Vudu!


I did a little more work on the bike this morning; I replaced the fuel line with clear vinyl line, tore into the strainer and started the work on the forks. Pictures:


(Got the wrong size outer diameter hose but I made it work.)


Strainer; was DEFINITELY a pain in the rear to remove. Once I got it removed, i found alot of gunk but I don't think it terribly affected the flow of the oil, just restricted it a bit. It hadn't been looked at since it left the dealer brand new since it still had the paint over the copper gasket!






Finally I am working on the forks now. I have run out of time to do more, but I am midway done with the work. I took the valves off and popped the drain bolts.....to no fork oil. "great." I think to myself as I am now looking at the cylinders for damage. None, PHEW! A little coaxing up and down of the fork tube and a thick grease substance crawls out of the drain hole followed by the proper liquid stuff. Both sides had this.





I assume the last picture that the little metal tube is the preload spacer from factory?

Also, can the fork seals be removed while the forks are on the bike, or do I need to tear the forks off and pull them apart to change the seals?

Also, i already designed slider pucks for the front solid axle and the rear axles WEEE! Haha.

[vudu]

Given the thick grease, may be worth remove, dismantle, clean, reassemble, fill, install. Takes 10 min to remove the forks from the clamps, including removing the wheel(usually). Just lay it out in order.
And that looks like a preload spacer if my DT's are anything to go by.

And while were on suspension I found that Koni (Ikon) have a shock. Cant remember from where but:-
Koni 3014 Single shock absorber (mono shock) for Yamaha XT400 1983-84, XT550 1982-84.
C/c length max 487 mm (˜19.2"), min 420 (˜16.5").
Delivered with progressive black spring (290-34/42/60).

Hope that helps

[XTwarrior]

I'll look for a link for that vudu.



Bumping because of the fork seal question. If I can get them out and put the new ones in without tearing the forks down that'd be great. I just dont have the room (I'm doing all my work in an 8x10 shed lol) or the tools to tear them down yet.

[G600]

Originally Posted by vudu

Hey xlv,
"So how can i tell if i have a CDI problem or if it is just the carbs that makes the bike cut out in higher revs"

You can do what i did and replace all the cheaper parts first. Regulator, coil, new battery. My symptom is a miss at idle resulting in a squeak when the plug doesn't fire. Goes fine at speed. I've ordered a Hyperpak. Patiently I wait.....

Previously I had the shop reset the float level and clean the carbs. $100 well spent.

Maybe I should point out that there is no need to replace the regulator/rectifier or battery when trying to solve running problems. The ignition circuit is separate and does not use the regulator/rectifier or battery.

It is not possible for an amateur to check the CDI unit. If you guys want to avoid buying a CDI unit only to find out that your old one was not the problem, you need to borrow a CDI unit or build a simple one for testing.

I built a simple analog CDI unit to verify that my original CDI unit was indeed shot. If you have some experience with electronics or have a friend that has, you can build a test CDI for very little money. See: http://www.transmic.net/en/analog.htm

[clc3251]

What's up with that?

[Zecatfish]

Originally Posted by clc3251

What's up with that?

Thats the Choke. There is suppose to be a cable there to the bars.
Just a note, the TT600 uses a pull knob for the choke, if you can find one.
I had to put a piece of silicone hole around my choke cable to make the clamp hold it secure enough.

One more note, I just remembered looking at that picture. Once in a while sqeeze that 90 degree nipple back into the petcock. I had mine fall out once. Quick squeeze with the pliers and it was good to go again.

[XTwarrior]

Originally Posted by Zecatfish

Thats the Choke. There is suppose to be a cable there to the bars.
Just a note, the TT600 uses a pull knob for the choke, if you can find one.
I had to put a piece of silicone hole around my choke cable to make the clamp hold it secure enough.

One more note, I just remembered looking at that picture. Once in a while sqeeze that 90 degree nipple back into the petcock. I had mine fall out once. Quick squeeze with the pliers and it was good to go again.

Lol yea, I guess the pull choke was destroyed in the accident, so the PO just made something work haha.

As for the petcock nipple thingy, mine has fallen out several times, and the petcock is now bad. I only get fuel when it is on resevere. I was screaming down the PA turnpike and all of a sudden she dies. No fuel in the line but swapped over to reserve and we were good to go. Ever since then it won't drop fuel in the line unless on reserve.