Leans out and screams

[jwhiteker]

I have a 1987 KDX200 that has been sitting for 2 yrs. I drained old fuel, disassembled carb and cleaned. New fuel 32:1, changed crankcase oil. Bike fired up fairly quickly but didn't want to idle well. Adjusted idle screw and seems ok. Warmed the bike up while on a stand and it started screaming at super high rpm. So high that the kill switch wouldn't stop it. I assume it's because the high rpm and heat was letting it diesel. Not good. Not sure how this happens with throttle closed to idle position.

So, I've repeated this issue twice and I fear that it's doing engine damage. But now I'm wondering what is making it lean and scream. Can crank seals do this? They've never been replaced. Just wondering what I should check first and how far should I go with this. The bike is in great shape and has always been kept inside.

Stock jets. Needle clip at top notch. Everything is factory. No mods besides sprockets. Any help would be greatly appreciated. I'm fairly handy. Lost my Dad a few years ago and I'm fixing the bike for my son to ride. That's 3rd generation riding this bike since my Dad bought it new in 1987.

[Goofaroo]

It could definitely be the cranks seals or an air leak somewhere else. Check the intake for cracks in the rubber.

[jwhiteker]

Ok. I kind of wondered about both of those options. I can see some dry rot in the intake boot and the reed holder. I wonder if any kind of rubber conditioner would help. I can't see spending $200-300 for these two pieces. And crank seals are probably a little out of my league. I may take it somewhere. Is a leak down check the proper method to see if crank seals are leaking?

[KDXGarage]

https://www.ebay.com/itm/114157762261?h ... SwwcJeeWLu

https://www.ebay.com/itm/224150825145?h ... SwXjxebn4W

There are two different user names selling such parts on eBay. The pictures look the same, so I am not sure if it is the same guy or not.

Pressure and vacuum tests would help determine seal condition.

Please be aware that it is a 34 year old motorcycle, so a lot of the rubber parts will possible be less than new condition, especially ones that had gasoline on them.

Air leak makes it rev up.

[jwhiteker]

Thanks KDX garage. I did see these items. I just can't see diving into a bunch of expensive parts for this bike, but I may have to. At least those two rubber pieces. I work on jets and we have some amazing rubber conditioners that I may try. I believe they seal up the pores quite well. Stay tuned. May take me a couple weeks.

[KDXGarage]

wrap the **** out of it with electrical tape and see if it still does it. If not, then there's your problem. Just remember, it's electrical tape, not gasoline tape. :-)

[jwhiteker]

Hey, that's a great idea. Thanks.

[KDXGarage]

I wouldn't head out to the deep woods like that, but it might work for testing purposes.

If it cracks apart on the inside, it will be an instant disaster when a chunk gets in the engine, so be mindful of that when applying stuff to the outside.

[jwhiteker]

I wouldn't head out to the deep woods like that, but it might work for testing purposes.

If it cracks apart on the inside, it will be an instant disaster when a chunk gets in the engine, so be mindful of that when applying stuff to the outside.

Good call. Yes, I would do it just to test. Not a permanent fix for sure. I actually almost destroyed the engine as it was by leaving a dropped screwed washer behind the air filter. So glad I saw it was missing from the flange and went looking for it. I also thought about wafting a propane torch around the intake boot and reed cage. We used to use it to find vac leaks on cars. I feel like I'm going to need crank seals because that's the most difficult possibility. Lol.

[Goofaroo]

You’ve got a really fun bike that would provide years of reliable service if you take the time and spend the money to properly repair it. If it has been stored inside and is in good cosmetic and mechanical shape it is not only a very capable bike but it also has more monetary value than you may realize.

Part of the beauty of the air cooled models is the simplicity of the engine. If it were me I would begin by pulling the carb, the intake boot, and the airbox boot. Thoroughly inspect them and see what you have. There is a possibility that they could be repaired. My boots were both in fairly decent condition except for a few cracks. I repaired them with Plastidip and 10 years later it is still going strong.

With the intake off you can devise a way to do a leak-down test and get to the ground truth about the condition of the crank seals and case halves seal.

If you really want to bring this motor back to it’s original glory you will need to pull it apart and check the piston and cylinder as well as the power valves, bottom end bearings, etc. A service manual would be a good investment and there’s plenty of help available on this forum. If you have the inclination to repair this bike it is certainly worth the time and effort.

[jwhiteker]

Hey Goofaroo,

I appreciate the wisdom and the tips. I had never thought of plastidip. What a great idea. I would assume application to the outside only? Also, sounds like a leak down check is in order. I'll have to research the procedure for that.
And yes, after looking around a bit, I can't believe these old bikes are worth as much as they are. I think I'll at least keep it in running condition and do whatever it takes to get it back to that state. After all, this bike has been in our family since it was new. I'm comfortable doing most maintenance and I'll probably at least clean power valves and pull the cylinder and look things over. Like I said, crank seals I may take somewhere else just to ease my anxiety.
My Dad was always team green and I always wanted Honda stuff. But I've been blessed by inheriting the KDX and a Prairie 360 4-wheeler. I will look for a proper repair manual. I found the original KDX owners manual and stuffed inside the front cover was a legal pad page where Dad listed every bike he owned, beginning with a 1969 Hodaka Super Rat. I really miss him. Motorcycles were his lifelong passion. Thank you for the support and kindness here in the group. I know how tiresome it can get when you are answering the same questions on a regular basis. I do try to search the threads before posting, but sometimes I still have questions and you all have been great to answer them.

- Keep your wheels on the ground, and your feet on the pegs.

- John

[KDXGarage]

Great post Goofaroo and jwhiteker.

When new, the bike came with an "Owner's Manual & Service Manual", lime green cover. Is that what you have? Clymer also makes / made a service manual for 1983 - 1988 KDX200s. I have it, and it is quite handy.

Don't feel like you have to have it running by this weekend. It has a few issues, but they can be repaired over time.

[Goofaroo]

Hey Goofaroo,

I appreciate the wisdom and the tips. I had never thought of plastidip. What a great idea. I would assume application to the outside only? Also, sounds like a leak down check is in order. I'll have to research the procedure for that.
And yes, after looking around a bit, I can't believe these old bikes are worth as much as they are. I think I'll at least keep it in running condition and do whatever it takes to get it back to that state. After all, this bike has been in our family since it was new. I'm comfortable doing most maintenance and I'll probably at least clean power valves and pull the cylinder and look things over. Like I said, crank seals I may take somewhere else just to ease my anxiety.
My Dad was always team green and I always wanted Honda stuff. But I've been blessed by inheriting the KDX and a Prairie 360 4-wheeler. I will look for a proper repair manual. I found the original KDX owners manual and stuffed inside the front cover was a legal pad page where Dad listed every bike he owned, beginning with a 1969 Hodaka Super Rat. I really miss him. Motorcycles were his lifelong passion. Thank you for the support and kindness here in the group. I know how tiresome it can get when you are answering the same questions on a regular basis. I do try to search the threads before posting, but sometimes I still have questions and you all have been great to answer them.

- Keep your wheels on the ground, and your feet on the pegs.

- John

Just clean the boots and then scuff them with coarse sand paper and wire brush. Tape it off so you’re only spraying the outside. Just follow the Plastidip directions and apply a few coats. As I recall I used about 5 coats. 10 years later it’s still holding up and is still pliable.

[jwhiteker]

Great post Goofaroo and jwhiteker.

When new, the bike came with an "Owner's Manual & Service Manual", lime green cover. Is that what you have? Clymer also makes / made a service manual for 1983 - 1988 KDX200s. I have it, and it is quite handy.

Don't feel like you have to have it running by this weekend. It has a few issues, but they can be repaired over time.

Yes, I do have that original owner and service manual. It just seemed really vague and poorly put together in my opinion. It's okay for some things but pretty weak at explaining certain common problems and solutions.

[KDXGarage]

Yeah, it is not a beginner's guide to every possible task. I wish. :-) The 1988 and later models came with a much thicker manual.