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Old 08-10-2012, 05:45 PM   #3001
Lenz1
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Quote:
Originally Posted by xt4ever View Post
Please, could you double-count your sprockets? Your numbers are sound very strange to me... Are we talking about a 520 conversion?
Gearing Ratios 101:

15/50 = .300 (less revs, more speed) 14/47 = .298 15/51 = .294 14/53 = .264 (more revs, less speed)

The lower the red resultant number, the lower the gearing ratio ie more revs , less speed , more immediate torque , more wheel spin
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Old 08-10-2012, 06:19 PM   #3002
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I was reading the manual i just bought and to adjust the float height you need a flaot bowl with a working drain screw. Mine is striped out. Anybody have a spare float bowl? PM me

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Old 08-10-2012, 06:47 PM   #3003
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Quote:
Originally Posted by NordieBoy View Post
TT350 comes stock with 15/50

I've got 14-15-16 fronts and 47-50-52-53 rears to play with.
Ah, TT350, Ok, I was talking about a XT350 converted from 428 to 520
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Old 08-10-2012, 11:19 PM   #3004
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Quote:
Originally Posted by xt4ever View Post
Ah, TT350, Ok, I was talking about a XT350 converted from 428 to 520
Which is basically the same except, in theory, the TT has a little more grunt so can push slightly higher gearing.
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Old 08-11-2012, 09:48 AM   #3005
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Originally Posted by NordieBoy View Post
Which is basically the same except, in theory, the TT has a little more grunt so can push slightly higher gearing.
It would be there, not here (europe) where the XT cames with stock 19/52, nor USA where she cames with stock 19/55. Both with 428 chains. Very different than the TT, which always comes with 520 chains and a very different sprocket ratio much more oriented to off-road
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Old 08-11-2012, 11:29 AM   #3006
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XT350 Mods

Even with the stock shock spring, you need to beef up the front suspension with stiffer springs so you may want to do that before putting a stiffer spring on the back. There are almost no aftermarket parts for the XT. I used the stiffer 1/2 of a GB 500 spring and the stiffer 1/2 of an XT spring and it worked fine.
Donnie from B&B Yamaha in Lancaster, PA did my shock back in '94. He took out the stops, increased the rebound damping, and added a remote nitrogen reservior that I ran at 200 psi with the preload maxed. Much less expensive than a new shock. He knows a lot about these bikes as he used to MX a TT350 (with its better carbs and suspension, hotter cams and higher-comp piston, it's a much better off-road bike than the XT).
AFA as the stock cam chain tensioner, I put 35,000 miles on my XT350, pulled the valve cover for the first time at 38,000 (tough) miles and the cams, tensioner, and valves showed no discernible wear - not even 0.001". With the slip-on, and fatter jetting (XTs are notoriously lean from the factory and known for carb boot leaks that make them hard to start), you'll notice a big increase in power. They make 25 rwhp stock and 30 hotted to TT specs and should pull to an indicated 95-100 mph if you have it jetted right. Arias made a higher comp piston and StainTune made a larger head pipe, both for the XT. They're the only other ways to squeeze more power out of the XT without compromising its bulletproof reliability. Have fun. When they're right, they are a blast on or off-pavement.
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Old 08-11-2012, 02:11 PM   #3007
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Boots installed just a bit of loping

I replaced the intake boots on the 89 and the coughing has stopped and it will even idle now. Runs much better. If I were to show you to ole boots you would wonder how it ran at all.

Ok it runs good and is quite livable but I am getting a little loping when the throttle is in that area where it isn't decelerating and it isn't accelerating. That free loose place right off of idle. If I keep the rpm up by downshifting no problem but if I am on a flat in the loose position I am getting a loping feeling. Maybe a little carb cleaner but do you guys have any idea what this may be?

thanks
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Old 08-11-2012, 03:02 PM   #3008
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Quote:
Originally Posted by xt4ever View Post
It would be there, not here (europe) where the XT cames with stock 19/52, nor USA where she cames with stock 19/55. Both with 428 chains. Very different than the TT, which always comes with 520 chains and a very different sprocket ratio much more oriented to off-road
The XT comes with the 425 here too.
The TT is the same as a 520 conversion on an XT.
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Old 08-11-2012, 03:06 PM   #3009
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Originally Posted by backroadbob.com View Post
They make 25 rwhp stock and 30 hotted to TT specs and should pull to an indicated 95-100 mph if you have it jetted right.
A whole day on a dyno and we got a TT up to 23 rwhp.
It was running 18 at the start.
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Old 08-11-2012, 07:53 PM   #3010
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Quote:
Originally Posted by NordieBoy View Post
A whole day on a dyno and we got a TT up to 23 rwhp.
It was running 18 at the start.
Measured differently I believe. Yamaha rated them at 27HP stock in the US so 25hp is a pretty likely #.
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Old 08-12-2012, 05:44 AM   #3011
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Originally Posted by NordieBoy View Post
A whole day on a dyno and we got a TT up to 23 rwhp.
It was running 18 at the start.
Nordie I can send you the shots of the oil cooler by email - I've already sent you an email

I'm expecting an ugly time with upgrading the carbies after an engine refresh including:

- new rings
- very lightly honed bore
- refaced valves and seats
- major inlet ports gas flow around valve plus port entry matched to carby ID @ 28mm & tapered into the valve bowl
- exhaust ports gas flow around valve bowl
- cyl head skimmed 0.020" (~ 9.7 : 1)
- exhaust headers opened at the first internal weld (significant ID restriction here) to match header pipe ID
- exhaust headers to cyl head join strengthened externally with additional pipe casing thickness

Yet to do is to change the carbies to re-align them with the centreline of the inlet ports etc and to mount the dual oil coolers off the existing auxillary oil cooler lines.

Nordie your experience with the dyno and fuelling upgrade would be very helpful.

Lenz1 screwed with this post 08-12-2012 at 05:51 AM
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Old 08-13-2012, 04:28 AM   #3012
NordieBoy
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Originally Posted by Lenz1 View Post
Nordie I can send you the shots of the oil cooler by email - I've already sent you an email
Go for it.
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Old 08-13-2012, 04:29 AM   #3013
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Originally Posted by Lenz1 View Post
Nordie your experience with the dyno and fuelling upgrade would be very helpful.
You may not want to know what we went through to get the best out of it though
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Old 08-14-2012, 04:30 AM   #3014
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Originally Posted by NordieBoy View Post
You may not want to know what we went through to get the best out of it though
With the odd std inlet setup - eg the carbie "boots"/joiners etc, the inlet flow would have all sorts of ups and downs across the rev range. I'm hoping to improve the inlet and exhaust flow significantly so some idea of what to adjust for the corresponding rev / load range would be a very useful start point for the carbie adjustments.

There is of course the possibility that said carbies provided far too much "amusement" and were eventually torn off, thrown at the wall and replaced by Mikuni's.

Enlighten me Sensai
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Old 08-14-2012, 01:47 PM   #3015
NordieBoy
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Quote:
Originally Posted by Lenz1 View Post
With the odd std inlet setup - eg the carbie "boots"/joiners etc, the inlet flow would have all sorts of ups and downs across the rev range. I'm hoping to improve the inlet and exhaust flow significantly so some idea of what to adjust for the corresponding rev / load range would be a very useful start point for the carbie adjustments.

There is of course the possibility that said carbies provided far too much "amusement" and were eventually torn off, thrown at the wall and replaced by Mikuni's.

Enlighten me Sensai
It started out with an aftermarket pipe, bigger headers, removed snorkels, drilled airbox side etc...

This is a race bike. XR400 front end and YSS fully adjustable back end.

At the start of the day, it had about 18hp at the rear wheel.
They ended up running the stock pipe, snorkels in, airbox side covered up and leaned off quite a bit, for 23hp.

You could just stare hard at the carb settings and the a/f would change.

The consensus was it needed valve and cam work to do anything more.

I want to replicate the jetting on my bike and see if the dyno chart is similar.
I have a feeling those settings will be totally wrong for my bike though.
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