Yamaha yz 250 1991

r91
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C, PA IT
8/13/2023 12:59pm
ace402 wrote:

How well do the forks work on the old chassis?

Forks works great, but it is slightly longer than standard and much harder as setting so the bike is a little rotated backwards. I think that the chassis has already more angled fork head respect modern bikes and agility and rider position is not the best with this setup. 

I tried to have more front height and reduce a little bit rear sag , and this changed already the bike behavior but for sure I need a slightly softer front spring and rise a little more the rear.

The worst thing of this bike are for sure the footpegs.

1
TooOld4WFO
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Fresno, CA US
8/13/2023 5:24pm

Fahrenheit.

At that temp you could conceivably take the item out after an hour and be done. Of course as the guide says I use the H series. I honestly do not think any of the non catalyzed series are as hard. 
I almost always leave parts in the oven for 2-4 hours. I shut off the oven and let the parts cool in there usually overnight. 
 

 

1
r91
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8/23/2023 4:55am

IMG 2713.jpeg?VersionId=PEqmiZUrG98C6Clutch installed

2
1
8/23/2023 7:57am
r91 wrote:
Clutch installed

IMG 2713.jpeg?VersionId=PEqmiZUrG98C6Clutch installed

Looks like your missing a bolt on that stator flywheel cover 

1

The Shop

r91
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8/24/2023 5:33am
r91 wrote:
Clutch installed

IMG 2713.jpeg?VersionId=PEqmiZUrG98C6Clutch installed

Looks like your missing a bolt on that stator flywheel cover 

Yes removed it to mount the clutch 😂

HackMan162
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Austin, TX US
8/24/2023 8:56am

Looks like your carb boot is not seated very well.

1
r91
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8/25/2023 4:59am Edited Date/Time 8/26/2023 12:42am

IMG 2735.jpeg?VersionId=HtgMp3DEaffPOn
Restoring a bike is stressful 😂

I mounted the oem silencer and realized that the exhaust is not the 1991 but probably the 1990 or older so the two parts doesn’t match. Now I have doubt if modify this exhaust (need to cut a little the final part) or try to find its own ( difficult to find in good shape).

 

2
TooOld4WFO
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8/27/2023 4:31pm Edited Date/Time 8/27/2023 4:33pm

That bike looks incredibly good to me. I really wanted to do the pink/magenta set up of the YZ vs the teal for my WR. With those black rims just simply stunning to me. Damn me and my need to look stock and original. I have to restore these older bikes with the broadest appeal. Great job and I love the look.

 

Your photo composition was excellent. You must have some background in photography as most wouldn’t have composed their shot like that.

1
r91
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C, PA IT
8/28/2023 10:12am Edited Date/Time 8/28/2023 10:12am

IMG 2754Yamaha copied my setup for the 93 bike of Chiodi at VMXdN… standard bike, black rims and kyb techinical touch on front with new brakes 😏😏

i’m curios about rear shock

3
r91
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C, PA IT
10/6/2023 1:58am

Question for the user. Someone has experience with GPI racing radiators? It worth to buy them or the quality is low? Are they enough well done to match plastics etc?

 

r91
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4/4/2023
Location
C, PA IT
10/12/2023 7:54am

IMG 3341 0  
in the end I bought a set of GPI radiator. From first look seems solid, let’s see if they fit and cool the bike properli. At least all the fixing points are much stronger than std radiator that are broken already

r91
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4/4/2023
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C, PA IT
10/13/2023 1:24am

IMG 3346.jpeg?VersionId=2Finally I got also some modern size footpegs, one of the worst thing in the 1991 standards

r91
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C, PA IT
10/30/2023 9:05am

Since last time I used the bike passed few months. I drained out the fuel but unfortunately seems like was not enough. The oil solidify in the main jet and also in the secondary and it was quite difficult to cleaned out properly.

image-20231030165825-2

Before I realize that carburetor was completely stucked i tried couple of kick and the kickstarter broke, causing a lot of problem to start up the bike when is cold.

Moreover now the bikes runs odd, It seems ok on the stand, but as soon as you make few laps start to run rich and not burn so much. Moreover every time I press the kill switch, it makes a big CIUFF from the exhaust.

I hope just something related to carburetor and not to the spark advance or electric/electronic.

Anyway I cleaned a little bit the engine, sealed everything properly, mounted new GPI radiators (Not the best quality but fitting was almost ok, just the left side is a little bit to big and almost touch the cylinder head), and new footrests.

 

WhatsApp Image 2023-10-30 at 16.37.18WhatsApp Image 2023-10-30 at 16.37.09WhatsApp Image 2023-10-30 at 16.37.02WhatsApp Image 2023-10-30 at 16.37.19

 

1
RussB
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991
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7/12/2014
Location
GB
10/31/2023 1:03am

My 89 RM250 had a Mikuni TM on as standard, and although the bike ran okay with the carb, I made improvements switching to a screw top Keihin PWK from a 97 RM250. I was able to get a better idle and generally stronger engine with this carb than the Mikuni.

I've since bought a shortbody PWK from a 08 which I'm going to blank off the TPS and Powerjet. Not tested yet but I'm confident this will be even better again. They pop up every so often for £1-200 so could be worth keeping an eye out for one

11/1/2023 7:10am

Yes I second ditching the old tm carb and going with a pwk air striker. The long body version is the screw top kind.

I put one of the long body pwk's 38mm off a 03 ktm 200. On my 91 ktm 300 much better. Starts easier idles better has better throttle response. 

Ktm's from like 99 up to 03 have the long body. 04 on have the short body. You want the ones with the quad vents. And the little wings on the intake side.  The ktm ones don't have all the added crap. Like throttle position sensors n such. 

r91
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C, PA IT
3/19/2024 4:31am

Some pictures 

IMG 5704
79b0db27-cbc0-42a4-986c-42f351f9eea9.jpeg?VersionId=NFZqIeEv1DShKPV2oqL163nff

fa833603-d340-4bf0-a28f-488a52c232a3

Snapseed

7F66C345-02AF-4D0D-802A-45540B9B92DD

 

3
CodyC
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62
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10/16/2023
Location
Morgantown, WV US
3/19/2024 6:09am

That looks legit.  I've always liked those era Yamaha graphics.  Do they have any clips on the petcock and carb on those models?  I'd be paranoid to go without them.  Also good call on the hydraulic clutch upgrade.  Once you pull one of those, IDK how you go back.

Inferno
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Location
Laguna IC
3/19/2024 6:10am Edited Date/Time 3/19/2024 6:11am

Great build mate!

It's a Ramirez stator cover? Very rare find!

Love this white/magenta YZ's...

Cheers.

 

r91
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C, PA IT
3/19/2024 8:58am
CodyC wrote:
That looks legit.  I've always liked those era Yamaha graphics.  Do they have any clips on the petcock and carb on those models?  I'd be paranoid...

That looks legit.  I've always liked those era Yamaha graphics.  Do they have any clips on the petcock and carb on those models?  I'd be paranoid to go without them.  Also good call on the hydraulic clutch upgrade.  Once you pull one of those, IDK how you go back.

Obviously there are clips on carb,  but they are black as well as on the fuel line I just tighthen with safety wire to recover some space

r91
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4/4/2023
Location
C, PA IT
3/19/2024 8:59am
Inferno wrote:

Great build mate!

It's a Ramirez stator cover? Very rare find!

Love this white/magenta YZ's...

Cheers.

 

Yep is a ramirez one, but luckily was on the bike since the beginning 

CodyC
Posts
62
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10/16/2023
Location
Morgantown, WV US
3/19/2024 2:24pm
CodyC wrote:
That looks legit.  I've always liked those era Yamaha graphics.  Do they have any clips on the petcock and carb on those models?  I'd be paranoid...

That looks legit.  I've always liked those era Yamaha graphics.  Do they have any clips on the petcock and carb on those models?  I'd be paranoid to go without them.  Also good call on the hydraulic clutch upgrade.  Once you pull one of those, IDK how you go back.

r91 wrote:
Obviously there are clips on carb,  but they are black as well as on the fuel line I just tighthen with safety wire to recover some...

Obviously there are clips on carb,  but they are black as well as on the fuel line I just tighthen with safety wire to recover some space

That makes sense I just don't think I saw it in the pic above.  Sweet looking bike man!

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