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New (to me) 1991 KDX250

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I am the new proud owner of a 91 KDX 250 :ride:

Looking around it seems its rough finding parts/plastic ect. for the bike.

Any advice from fellow owners on where to look/whats compatible (KX250 years)?

I'm looking for some new side panels or all new plastics for that matter and a new seat (aftermarket is ok, anywhere that I have found oem it has been overpriced).

Also any advice on upkeep & upgrades? I have read previous posts regading the forks and jetting but I'm good in those areas.

I'm looking forward to restoring it to its former glory 🙂

Thanks!

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Hi. Congratulations on the KDX250!

As best I know, there are no aftermarket side panels or a seat. OEM is the only choice. You might be able to fit a KX500 seat cover, but I have never tried it.

Look at the parts diagrams on the Kawasaki site, as it will show you which year models have the same part number.

General used dirt bike advice applies, such as checking bearings to clean inspect and grease.

It's a 19 year old bike, so look for worn rubber parts. You may want to consider getting the shock checked out, as most people just run it like a Monroe Gas-O-Matic and never do any service on it.

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I had the same bike. With careful setup, it makes a great woods weapon. When properly tuned, that engine has such great low-end torque that it would climb a tree if you could hang on.

Pay close attention to the rear wheel bearings and the lower shock bearing. Neither has a very long life.

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Thanks for the advice guys.

Yeah it looks like I might have an issue with the rear suspension or lower shock bearing aftet making some adjustments. After loosening the rear spring (the guy I bought it from was 250lbs and was maxed out) there might be an issue with the rear shock absorber. It is not respoding like it should be, might just need more adjusting with more inspection.

I just took it for my first ride after replacing all the fluids, draining the tank and replacing the sparkplug (Bosch R3 Platinum +4 ?!) with a NGK BR9ES. It fouled the plug in about 2 hours at LOW rpms going down a tight single track hill. He told me when I bought it that he was running 50/1, I went with what I usually run 32-40/1 with Honda HP2 oil.

So I assume it is running to rich, my next question would be:

Can I just adjust the needle without replacing the jets (we want to ride tomorrow :busted: for a short term fix? or should a hold off and replace the jets and needle? I am a old time rider just puttsing around at 1K - 5K Ft. 50-90F at the moment.

Thanks!

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To check the bearing that supports the lower shock mounting bolt, put the bike on a work stand, then loosen the bolt. Before you remove it, you can make it easier on yourself by using your right foot to lift the rear tire a little as you remove the bolt. It is a high wear bearing that many riders neglect, unfortunately (for the next guy in line like you). :busted:

You might want to try an NGK 8 heat range plug first. I have a 1994 KDX200, which comes with a 9 standard. The trails I rode on were so tight that I couldn't keep it burned off. I switched to an 8 and went from fouling a plug a day to a plug a month. I was then able to make educating changes on jetting.

I think 32 - 40:1 may be better for it.

You can adjust the needle without changing the main or pilot. I strongly suggest you try the B8ES (or BR8ES if you would like) as your first change.

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For summer mountain riding (1500-2500 ft.) I ran a 38 pilot, the next leaner OEM needle (sorry don't remember the number anymore) in the second to top position, I think a 152 main, and a leaner slide. You will never get the jetting very clean at small throttle openings without the slide. Even a 35 pilot (the smallest available) will be too rich with the stock slide. I also ran a BR7ES plug, because many of the trails I rode on were just too difficult and technical to push the engine hard enough to produce good combustion temperatures. The 8 plug was a little too cold.

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Warm up that combustion by using more oil in your mix and leaner jetting of course. I used 50:1 ONCE in my bike and it fouled a plug. First plug foul ever to me in three years of riding. I'm getting hotter temps at 24:1 and ride Washington's finest mountain trails on a 2 smoke MX bike.

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Warm up that combustion by using more oil in your mix and leaner jetting of course. I used 50:1 ONCE in my bike and it fouled a plug. First plug foul ever to me in three years of riding. I'm getting hotter temps at 24:1 and ride Washington's finest mountain trails on a 2 smoke MX bike.
Yes, I should have touched on that. I ran 26:1 in my KDX250.

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Thanks again for the advice guys.

24-26:1 check..

I will run a BR8ES first and I bought a BR7ES to carry along with me tomorrow.

I have plans to replace the lower shock bearing this week but after inspecting some more today it appears that I need to check the gas pressure on my rear shock absorber.

When I got the bike the spring was maxed out like I said and then I adjusted it a little to extreme the other way so I went back and did it again to a happy middle point but after all the adjusting it doesn't appear to be springing back into place like it should be. My son's KDX200 has more height then my 250 now. If I lift the fender up it will hold the height it should be at for a minute or so and then slowly sink.

Could all the adjusting of the spring put a strain on the shock absorber and caused this is? Have any of you had yours filled (nitrogen) or had issues with it?

Thanks!

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Do NOT "check" the nitrogen pressure. The volume in the bladder is so small, even the amount you will lose with a pressure guage will be enough to render the shock useless if you ride. The pressure won't get low, it will either have full pressure or none. If it has none, the shock will perform very poorly, you will know something is wrong. It will have little to no damping.

Your issue with it extending very slowly is either the rebound adjuster cranked all the way in, or the linkage/swingarm bearings are dry and binding.

The spring rates from the factory were very unbalanced. The shock is sprung for about a 200 pound rider, while the fork springs are too soft for anybody over about 150 pounds. Replacing the fork springs should be one of your first mods, it will absolutely transform the handling and control. I ran .43 kg/mm springs in mine, I weigh 175ish pounds.

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Yes, DO NOT mess with the nitrogen in the bladder. It is not like a car tire with a huge volume of air compared to a baseball sized bladder.

It's old and it probably has worn seals, which allowed oil to leak out. The pressure will drop in a bladder over time also. If it is like most people, the last time it had fresh oil was when a friendly Japanese person put it in for the first time.

Beyond the commonly neglected area of bearings, you may want to have the shock inspected and fresh oil and nitrogen installed.

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I greased the bearings and tightened the spring back up and it is ride able until I can get in and replace the bearings, spring and get some fresh oil & nitrogen.

I am low on funds so instead of replacing the clutch cable (which was sticking as it was released) I bought a cable lube tool and some cable oil, what a world of difference. Anyone on the fence if this makes a big difference on an old bike I can tell you it works like a charm if your cable isn't frayed.

I also neglected to check the brake fluid on the front brake and it completely went out on me. I got home and replaced the fluid. Props to this site again on the advice about bleeding the front brake, I ended up having to blow fluid through a tube into the bleed valve which I read here. I swear I could have pumped that thing for hours and it still wouldn't have built pressure (btw: a fuel tank breather hose fits the bleed valve if you have one lying around, after cleaning it).

Went out riding tonight and after about 15 minutes the front brake locked up. We opened and shut the release valve and everything was back to normal, still good pressure on the brakes. Is this normal? Can the pressure build after replacing the fluids on the first ride after things get hot or am I looking at more issues? I was obviously hesitant with the front brake after being almost thrown but there were no more issues for the rest of the ride.

I also replaced the kill switch :busted:

I am new to working on bikes so hopefully this thread can help someone like me in the future :banana:

Here is a picture of the bike after some cleaning, I will update as I go through things and get it back in shape 👍

Thanks!

John

KDX250.jpg

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The front brake locking up means it's getting hot and building pressure. You'll most likely find that the caliper pins are either dry, grooved, or both, preventing the caliper from sliding freely and causing it to drag and get hot.

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