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Discussion Starter #1
I got this turd about 4 years ago in trade. I made money on the deal until I tried to get this piece of crap road worthy.



So far I've redone the whole rear subframe to match sr500 dimensions(way lighter though), 36mm tx750 front forks, rd400 front caliper, xs650 front wheel, xt500 tank, custom exhaust, custom seat, etc.

I am planning shocks about 1" longer as well as some linear springs and cartridge emulators up front. I've got a newer set of tires to put on, but these will do for the time being. Lights still need wired in but it's a relatively simple circuit with only a lighting coil running through a regulator. It also needs a inner rear fender extension and some side covers but I'm going to ride it and tinker as I go along. Uni filter not seen in pic, but I've got filtration and eventually plan a 34mm Mikuni since this one is pretty worn.



 

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Discussion Starter #4 (Edited)
Early xt are steel. I had an aluminum tt one that came with it, but it's super rough. The nice ones fetch way more money than I am willing to spend so I re-did the mounts for the earlier tanks and got a cheap steel one for now. I really wanted to do a polished tank, but it's like $400 and up to play ball.
 

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That's cool. Is that a stock swingarm? I think they had aluminum swingers in '80 or '81, but earlier would be round steel. The "4 valves" sticker on the tank is funny.

You should try and find a Mikuni 38, that's what we usually run on flat trackers. Speaking of which, not sure about Arkansas, but I know there's some flattrack racing in Kansas. You should see if there's a track with a vintage class near you, go out and give it a try.
 

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Discussion Starter #7 (Edited)
That's cool. Is that a stock swingarm? I think they had aluminum swingers in '80 or '81, but earlier would be round steel. The "4 valves" sticker on the tank is funny.

You should try and find a Mikuni 38, that's what we usually run on flat trackers. Speaking of which, not sure about Arkansas, but I know there's some flattrack racing in Kansas. You should see if there's a track with a vintage class near you, go out and give it a try.
Stock swingarm, this is an 80. I don't know who put the stickers on the tank but they are clearly from the later model xt bikes. I think it's pretty funny as is and it seems not many people notice it. Eventually I'll order some factory styled decals and redo it.

The 38 is probably a bit big for my stock motor. I've tossed around the idea of 36 or 34 and unless I hop this up any, the 34 should probably be acceptable. I may lose a bit on top end though.

As far as flat tracking goes I'm still a ways out from any venue. I will be out in Daytona in a couple weeks though for some AMA viewing pleasure.
 

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Good point, almost forgot that most of the flattrack bikes are punched out to 540.

Have a blast in Daytona. I went last year for my first time, what a fun scene.
 

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Discussion Starter #9
Good point, almost forgot that most of the flattrack bikes are punched out to 540.

Have a blast in Daytona. I went last year for my first time, what a fun scene.
I'll only be there a few days, but while there going to see the final day of flat track and the Daytona 200. Should be fun I think. I'll pass on all the other "pageantry'.
 

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We endurance raced one of those with a KZ650 front end on it. Even with the stock KZ caliper and disc it had plenty of brake. Stick a big disc and 4 piston caliper on it and it will be great. Personally, I don't like the power of a 540. It just revs a little too slowly and the power is in the wrong place for roadracing, it might be great on the street or a dirt track. There are some cool SR/XT/TT parts on the for sale page at VFT.org.

Enjoy it, thumpers are cool.
 
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Discussion Starter #13
Apparently the banjo bolt for the rd400 front caliper is a m10x1.0 vs. standard 1.25. I managed to get the caliper reassembled with new seals though, so as soon as that's in I'll be ready to ride.

Also got a chance to mess with some spare Cb450 covers. I think they will do the trick with some trimming. I flipped them from left to right, but will still need to do a possible pie cut to get them a better fit.





 

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Discussion Starter #14
The titty gots some new shoes. Still waiting on the caliper banjo bolt. Got the rear brake switch functional, just need to finish wiring. Clutch cable won't work with the aftermarket perch, so I need to track down the OG one until I can get a fancy cable made. Was really hoping to run it around the block today, but it shall wait. I've got all the vm34 Mikuni stuff ready to order, totaling about $117 including all the necessary jets to get me close enough.

 

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Discussion Starter #15
I finally broke down and bought a Mikuni VM34. The stock carb was bananas from the get go, and getting a good reliable start cold was somewhere in the 4-5 kick range.

I decided to copy some average jetting data that has been posted with the 34 in hopes I could start out in a decent spot, so I went with the following:

main 230
pilot 27.5
needle jet p6
needle 6dh3 on the 3rd clip

Started up and idled on first kick.


Probably could still use some tuning, but I need to address the dragging clutch first as well as wiring up lights. Also need to get a Uni filter that will fit the mouth of this carb as this one is slightly larger than the factory.

Also got the front brake bled, so I can stop now too.
 

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Discussion Starter #16
It's been a good week. Got my antique tag/title taken care of and the Progressive shocks came in today. Hopefully the new clutch pushrod fixes my dragging clutch issue and I can do more than just a poke around the block.

 

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Discussion Starter #17
After a week chasing my tail, the clutch issue has been resolved with an NOS push rod. It was exciting to feel it finally allow me control of the clutch, so I started piecing together the throttle cable elbow for the vm34, and putting on the new UNI filter that has the properly sized opening. I kicked it to life, and took my first "real" test rides around the neighborhood.

First few impressions:

This thing feels so light and nimble. Definitely a plus.

Shocks feel a little stiffer, but I think it suits my riding style.

A little more ticking from the exhaust valves than expected. May have to do the grub screw mod.

From mid to full throttle the bike loads up and falls flat on it's face. Lots of popping on decel. I was thinking the main jet may be a tad rich, but I noticed a slight puff of air coming from the exhaust I made up. It was a factory drain hole in the kz440 muffler back when it was still double wall. I think this clearly isn't helping the popping, so it's first on the list before moving on to any other possible air leaks. The stock intake rubber is original, and the vm34 sits a little looser than expected until it's cinched down. I may find a new intake boot that suits the vm a little better, but for now just want to confirm it's sealing up tight.

Plug color is a lighter coffee more towards the rich side of the spectrum but that could be from the idle circuit. The electrode strap shows no major heat past mid strap, so I don't think I'm going lean anywhere.

I'm going to re-check timing with a gun and adjust accordingly.

Lights still need wired, but that shouldn't take much effort.

I think my master cylinder may be a hair on the small side. It's 11mm and I think 12 or possibly 13mm would give me a little firmer feel. After a few hundred test miles I should know whether it's going to need changed for sure though.







 

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I thought engine pop on deceleration was usually a sign of a Lean operating condition? and mid to full throttle falls flat on it's face would imply Lean fuel mix &/or late timing :confused:
… I guess the spark plug reading should clear that up, let us know what it takes to finally sort it out.
 

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Discussion Starter #19
I believe it can both ways from what I understand. Unburned fuel in the hot exhaust causes another "ignition" within the pipe. The hole in the pipe isn't helping either, as that can cause the popping.

I'm not jetting anything until air leaks are gone, timing is checked, valve lash re-checked, etc. I'll throw in a new plug and do a real plug chop after those are addressed. One thing at a time should sort it out. Luckily if it is just a main jet swap that would be a quick and easy fix.
 

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Totally off the cuff here; if you've changed the carburetor to a vm34 you should be able to just move the cir-clip one notch lower on the main jet needle. That will richen the mixture for the top half of your carbs throttle operation and quickly determine in it is too rich or too lean.

… I had bikes that required that adjustment bi-annually to accommodate for seasonal atmospheric climate changes.
 
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