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Two Stroke racing

Open class Desert racing.. Some Long Hard days of racing.. I wonder how that guys cylinder cracked?? Did not look like he crashed. Overheated?? 2 strokes lot of work to keep running but a ton of fun!! On the pipe!! Looks like they still race this Finke Desert..
Austen, Never done any dirt bike racing but I love the 2 strokes. Here is a pic of one of my Triple Triples. This one is a 98 Polaris XCR700. This one is sort of old school. 38mm Mikunis, round slide, case reed, High compression. Premium fuel, with the triple tuned pipes. Stock sled. No exhaust valves. It is a pipey machine. When it hits 6500 RPM hang on. It is a rush.. This one has that tin pipey sound also. Some of my others do not. :cool
I am currently working on an older 75 Yamaha GP433 reed valve motor. I looked it up and they still make Boyesen reeds for it. SO my plan is to get it running stock. Get another set of stock reeds, and put the Boyesen reeds on the stock cage. All I see is the carbon pedal reeds for it. Do a back to back comparison.. Should be interesting..

Triples Sound good also. Even the 4 stroke triples. Not many triple lawn mowers. LOL. I have worked on some Toros. Motor in back, deck in front. 3 cylinder gas powered. More of a golf course mower. It could do a backward wheele!! Give me a Kawasaki H1!! I would take an Suzuki GT550 ,I used to ride some.. I need to cool off and go work on my 12 HP single, Lawn Tractor..
 

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Discussion Starter · #22 · (Edited)
Those pipes! Those pipes!! Wow! :ThumbUp:
I'll bet that machine is a rush! I'm sure the sound of that triple is incredible. Thanks for the photo and detailed description! I have a sense of what it's like to ride. :cool I like that it's a none power valve motor too.

I'm sure you're going to love the Boyesen reeds. You'll have to report back once you get them installed.

Yes, those GT550s and H1s are cool bikes. Many have made them into drag racers.

I'm glad I found another such another diehard 2 stroke enthusiast!! They offer a totally, one of a kind, adrenaline pumping experience. I'm foaming drooling at the mouth just thinking about going for a ride! :sidelaugh
In regards to the race, yeah, I didn't understand what the cause was for the cracked cylinder. I also thought the part were the "dust was clogging up the muffler and slowing him down" was a little weird. I had never heard of the Finke race either.

Man, I'm hooked on these 2 stroke open class bikes!!! :ROFL I've got a CR500 planned for my future. I'd like to find a 1985-1986 CR500 and do a modern CRF450 upsidedown fork conversion along with rear shock and also convert the swing arm to accept a disc brake.

I could talk this stuff for hours. :sidelaugh :p

 

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Snowworks, you bring back some fond memories. I never had the money for those machines you mention myself, but I was lucky enough to have friends and relatives who did, and even luckier that they let me ride and use them. Gosh, I close my eyes and I can hear the sound of those 2 stoke Polaris sleds blasting across the snow, and that H1 down the road.
 

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Two Stroke Smoke

Thanks for the kind words Austen!! Yea, I like 2 strokes. Sounds like you do to. I like motors of all kinds, but 2 strokes make me smile :). Until they break.. If I lived where I could ride from home I might have a few dirt bikes and maybe an open class dirt bike.. Sounds like it would be a rush!! Till it threw me off!! It is enough to have to trailer my sleds to ride. Summer time I have other projects to do and toys to ride.
I forgot to mention that 700 is about 135 HP. Funny you mentioned about power valves. I have 2 other sleds that have power valves. 800 triple and a 600 twin. They are different power bands. They just have a linear pull. Start lower on the RPM and pull good till red line. Get better millage. Probably faster. But they do not have that sound!! Here is a pic of the two triple triples. The red 800 has Flat slide carbs and power valves 155 HP.:2th:
The Tatts Finke Desert Race is in Australia and been going on since 1976. I guess that is why I never heard of it. The Baja 1000 is one we hear more of. The Supercross is in Detroit this weekend. I have not been to one in a long time but the 4 stroke have that low down grunt sound. Not that two stroke sound of yesteryear..
Like you said I could talk about 2 strokes and motors for hours
 

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Discussion Starter · #25 · (Edited)
Better get your popcorn out because this installment is two parts in one. The first part consists of a series of more updates to the bike and secondly my first real exploration into the mountains with it.

Recently I took it out on a maiden voyage on some local trails with a co-worker who also rides. It was a good shakedown test to see if there was anything that I wanted to change before I took it on a trip. After the ride, I noticed that a couple of seals had blown where Permatex had been used so I placed an order with "Enduro Klassiker" in Austria that specializes in parts for vintage bikes like this and got an assortment of new gaskets where suspected gasket maker.

1. A nice trickle of smoke was puffing out from where the expansion chamber meets the head and sure enough the gasket maker had failed and blown out. The design of how the expansion chamber attaches to flange is not very good. It made sound weird, but using stretch and seal plumbing tape is what other owners swear by to use to solve the issue so that is what I did. No more leak.

2. Secondly, and more disturbing, I noticed some very small droplets of coolant starting to ooze out from the head "gasket." After I removed the head I found quite a few droplets of coolant scattered inside the cylinder as you can see in the photo below. It must have been losing a fair amount of compression here combined with the air leak in the exhaust; I'm surprised that it ran as well as it did. It most likely was burning some white steam mixed in with the smoke of the exhaust that I didn't notice. In any case, it turns out the head gaskets for these are made out of some extremely thin material, it is basically thinner than a piece of copy paper. This is why I it was tough to identify what was or wasn't in there before other than Permatex. I actually broke the one I bought when I was installing it so I said "forget it" and made my own new head gasket out of some very slightly thicker gasket paper.


3. Something else I came across which I thought was noteworthy. When I ordered all my gaskets for a '1986 KTM 500' the water pump gasket in particular, which I indeed verified is for a 1986, does not fit. After looking at some microfiches I discovered the left side engine/clutch/water pump cover is on my bike is off a later 1988-1996 500/550. I had to re-order a later style gasket so that it would fit. At some point early on in the bike's life, I imagine, the cover was swapped out for a later style. The original may have suffered bad cavitation early on and had to be replaced. When I opened it up, I did find some cavitation inside the waterpump so I did what was recommended to me on the KTM forum and filled it with a coating of JB Weld. The Evans Coolant prevents corrosion but I didn't want to leave the existing cavitation exposed. Someday when replacement covers are available I'll replace it with an aluminum version.

4. While the bike was torn down for a while I decided to change the graphics to green as seen in the photos below. I also purchased new OEM style Acerbis plastics from Andre (Enduor Klassiker) as well. I'll store the original plastics with the blue decals in case I ever want to go back to them but for now I really like the green.






5. I also found a good used four pot rear brake caliper on Ebay from a later year KTM that will swap over. I plan to also install a more modern front master cylinder to provide increased braking power and will do that all at once sometime.


6. I also installed a new front fender brace support which was an option for these bikes originally. I think it adds another little bit of retro bling.


I had to modify the mounting a bit for it to fit.




7. During the same time period in the 80s, some of the smaller CC KTM dirt bikes came with these cool, stylish, magnesium ignition covers. I found one on Ebay and took my chances with it in terms of fitment, however, it seems to have disappeared in the garage!! I don't know where it went and still can't find it.... sooo odd to lose something like this. Anyway, when I actually did have it in my hands I discovered that it has a slightly different mounting bolt pattern than a 500's (of course) which is kind of a shame. It would actually mount if you were to flip it upside down however but that wouldn't look right. Really the only way that I can see to make it work would be to cut the center out of the original cover which would leave you with a mounting ring that you could then glue onto the mounting surface of this cover. Voila. I would also shave off the mounting tabs on this cover if I did go that route. Might give it a try in the future if I'm feeling ambitious. If you have any other ideas in terms of how it make it work before it's too late, let me know!


 

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Discussion Starter · #26 · (Edited)
2nd part, The Trip!

Let's see if it all paid off.

In this part I thought it would be fun to sort of document the trip in sort of an ADV Rider style. It gets a little annoying stopping all the time, taking off my backpack to get the camera out so I didn't take a zillion photos but you'll get the idea.

Logistics
I realize most are not located on the west coast so this won't mean much, but the plan was to go riding where my dad and I have gone trail riding a lot back in the day near Lake Chelan. More specifically, over Cooper Mountain. It's about 4-1/2 hour drive from home. I was going to camp where we usually did too.


The plan was to drive to the camp site and stage there. It turns out our old super secretive camp site is now tent city. Definitely un-appealing in many regards. So, I decided I'd find another spot to camp while exploring on the bike so I staged temporarily elsewhere for the interim.



It didn't take long to realize that something had to be done to the tire pressure as traction was just not there, at all. This bike is like riding something that's on nitrous and has 1000HP underneath you. Giving it 1/4 throttle has the same effect as cracking the throttle wide open on a 'normal' bike only without having any lag, RPM build, up whatsoever. The power is just there instantly at any given point. I sound like a broken record here, but you really do almost ride this bike more off the gas than you do on the gas. Anytime you're on the gas you're basically in a full on drift, back tire squirling side-to-side while you're trying to counter steer the heck out of it. I ended up lowering the tire pressures down to single digits where the tires where almost spongy-balloon like; thank God for rim locks. It helped maybe 15-20%.


There were a few of these trails we used to ride that were now either overgrown or had a lot of downed trees. I had already crossed three smaller ones before I had gotten to this point and decided to turn around. The trail was increasinly getting narrower and narrower and I didn't feel like putting a ton of new pinstripes on the plastics and number plates.


This is more like it.


This is what I call the "burnt forest." It was quite an interesting sight. All of a sudden you just enter it. There was another person there taking photos too when I was passing through.





]

The 'look out. I had officially made it to Cooper mountain at this point. It was only 13 miles on the odometer but figured it'd be a good time to do a fuel check. I was almost dismayed to see that I was nearly at half a tank already! WHAT!?? If I had been on any of my former 4 stroke dual sports at I would have still had a full tank at this point.

I had a realization that because of the level of performance this thing pumps out, it's really not hard to understand why it goes through fuel so fast and I shouldn't complain about it either. You can't get both. This thing is not a dual sport, but that's not what I was hoping or wanting it to be either. I had kind of always thought it was my imagination when I'd notice a change in the fuel level after a short time running it a bit at home. I wasn't- it just goes through fuel that fast. These bikes came with an even small tank designed for MX tracks. This one has the large 3.1 but still has a limited range. I estimated it gets between 13-15 MPG.



I was feeling hungry and this seemed like a nice spot to stop. It is sure different that riding a four stroke going down hill because there's zero engine braking. I don't like coasting for long distances on 2 strokes without applying any throttle so it was a balance between using lots of brake input with little inputs of the throttle periodically at the same time.



Obligatory food pic.

Some pretty wildflowers.


Helmet hair! Helmet hair!! Nobody gets worse helmet hair then I do. If there was a product that lessened it, I would be the first in line.



Lake Chelan in the distance. The next goal was to find a new camping spot.


After some riding I decided to head down into Chelan to the "Lakeview Drive-in" to grab a burger for dinner. It was like spring break in Cancun, the beaches were filled college kids.

Nice view of Lake Chelan to eat your dinner.

Time to head back into the mountains to setup camp. I had found another, better, camp site that was more scenic than our usual. It was several miles further up a narrow and rough road where I had to go slow with the trailer.




The camp site.


Watched the sun go down.


And watched a movie before bed, haha.

I Didn't encounter any wildlife. There was a noisy owl that I heard at night and there was a wind that came through the trees that made a lot of noise. The spookiest part were three different cars that drove past at odd hours of the night. As my dad has always said, you sometimes have to watch out for the people you come across when you're out here vs. the wildlife.

The next morning I went for a short ride before I packed up and left. I found another trail I had never been on before and this one offered some long stretches that I could open it up a little.

Overall, a great trip! I have another one planned with my dad in Oregon in September. I'm sure in the meantime I'll post some more updates to the bike and maybe another ride report if I do another weekend trip with it.
 

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Awesome adventure!!! Those cars at all hours is not cool at all! Way world is today! You sleep in truck?
 
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Discussion Starter · #28 · (Edited)
Awesome adventure!!! Those cars at all hours is not cool at all! Way world is today! You sleep in truck?
Yeah, spooky for sure. Most likely people looking for a camping spot but it's eerie when it's pitch black out and all of a sudden you hear a car and see their headlights slowly coming up the mountain road at 2:00 in the morning.

I slept in the bed of my truck. Had a blow-up mattress and a sleeping bag. I love looking up at the stars. :2th:
 

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Discussion Starter · #31 ·
Wow! Beautiful bike, beautiful scenery! What fun!

Glad ya got the motor issue sorted out. You wouldn't want a breakdown in the middle of nowhere. Today 06:24 PM
Thanks,

Yeah, that was the goal. With a bike like this you want to bring tools along just in case in your pack and I did have to use them a couple of times on the trail when a couple bolts came loose.

The second two cars might have been heavily armed DEA agents seeing what the first guy was up to in the middle of the night. ;)
:sidelaugh

Maybe it was Jesse and Walt!
 

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Good Ride!!

Austen, Great trip you had!! Were you ridding alone? Glad to here your bike worked well and no break downs. Them 2 strokes do get thirsty. Most sleds have about a 10 gallon tank. It is hard to think that snow has so much drag. Wheels roll much easyer. With that 500, no power valve and on the pipe it will suck some fuel. Nice story!! :ThumbUp:
Not much time to post but have been busy working on motors and home projects!!
 

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Discussion Starter · #33 · (Edited)



During my on-going research of 1980s KTMs, I discovered some of the < 500 displacement CC models (it may have only been the 250 model... I don't really know for sure) came with these really cool retro looking, magnesium, flywheel covers. "Digital Control"- These things are awesome!! From what I've seen, this same cover was not ever offered on the 500 which was treated to a much more plain/basic plastic flywheel cover in comparison pictured on the right above. Being a sucker for things like this, I had to at least try to see if I could somehow make one of these work on my bike.

I did some research and these covers seem to be typically listed in the $50-$85 range and saw some listed well over a hundred on some independent websites. I eventually came across this guy going cheap for $19.99 because it had some corrosion issues so I figured it would be the perfect one to experiment with and chop up. The question was how I was going to do it- more on that. When I initially got it in my hands, I discovered the bolt pattern was wrong for a 500.... of course.... (although it would've actually mounted upside-down) and the cable guide slots that you see molded in it are non-relevant to a 500 as well. The good news is that the cover is the right size to fit over the 500 flywheel.



After looking at both covers side by side, I devised a plan to make one cover out of both of them. This would be done by cutting off the non-relevant cable guide portion of the magnesium cover; the cut was made where you see the white line. The stock cover would then be trimmed off and then the two would be joined together via epoxy. This way I would still have the correct mounting plate/face of the original cover to mount to the bike but have the magnesium cover (or cap now) for the front side.

The big question was how I was going to cut the magnesium cover in a professional (and safe) manner. Good luck taking it down to the local machine shop and paying them a quarter of your monthly earnings to make a single cut. I had remembered our good friend and member, Ellis, (tiretrx) who had helped me out with another project a few years ago. I hesitantly asked him if he'd be interested in taking this on fully expecting him to say "get lost!!" :Ugh: after I explained the good for nothing project to him but instead he said send it on over! I couldn't have done the project without him. One of the things that is so great about Ellis and his machining services is that he understands our hobby so he's willing to go the extra mile to help us out at realistic prices. I couldn't recommend him higher! Thank you again, Ellis!







Was it worth the effort?







You know, I didn't know how it was going to look after it was mounted on the bike. If it turned out looking like any one of my many failed arts & crafts projects when I was in grade school, then I had every intention for it to hit the trash and be replaced with a new plastic cover. The idea on paper was that it would sort of match the magnesium clutch cover on the other side. I think I'm happy with it, it's sort of a funny idea I guess. It would probably look more pronounced if it was repainted.

2. I purchased a new Dynoport "Big Barker" muffler from Rich Daly, the owner of Dynoport.



Out on my last ride in the mountains the brake rod ended up losing one of the mounting bolts which made it flip up and shoot a hole right through the fear fender locking the up the rear tire at the same time. I thought the motor locked up when it happened. As the rod shot up, it apparently also put a small dent in the rear end of the muffler which was unfortunate but it gave me an excuse to get a different one which I was tentatively planning. While I was out on the trail when this happened, I removed the rod from the bike and rode back to the truck using just the front brake and fortunately had a spare bolt and nut that was the right size so I could remount it and continue riding with both brakes. It proved to me the importance of bringing extra tools and hardware along for this bike.



Aside from the damaged rear fender (already replaced) and muffler, there was no further damage to the bike. The remaining bolt that had been on the brake rod at the time of the incident was tight and had a nylon lock nut on it but I'm guessing the one that worked its way out did not. In any case, I replaced the mounting hardware on both ends with new locking hardware as I don't want that happening again but will still be keeping an eye on them.


Surprisingly the new muffler really isn't any lighter than the stock one.

Made a new joint connection















The original muffler was not straight-through like this one so I was wondering just how much louder it was going to be. The tone itself didn't really seem to change but the "bang bang bang" is louder. It was loud before but now it hurts your ears standing next to it while it's idling.

3. Air filter fitment: Before my last trip, I did a visual check of the air filter and it looked nicely oiled and clean so I left it alone. I could tell that it was a dual stage aftermarket and not the original which I thought at the time was a bonus. After I got back from my last trip, I pulled the seat and it was dirty enough for a cleaning but as I was removing it I discovered that it sat against the air box too loosely. The problem was that the air filter was simply too big for this application. No matter how I tried, it just did not make a good seal even with filter grease. I wasn't thrilled when I found this out. I learned on a forum that Suzuki DRZ400 air filters will work as a replacement and I actually happened to have a stock DRZ air filter from when I had one of these bikes. I found the DRZ filter is indeed smaller than the aftermarket one so I put it on the bike and it is a much better fit and seals tight like it's supposed to.







 

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Okay, I'm kinda confused. You said the brake rod came off, but it looks like it's cable operated. Do you mean the lower strut rod that holds the caliper assembly in place?
 

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Discussion Starter · #36 · (Edited)
Okay, I'm kinda confused. You said the brake rod came off, but it looks like it's cable operated. Do you mean the lower strut rod that holds the caliper assembly in place?
That would be it, "brake rod" for lack of a better term.

Below is a line with an arrow showing the path that it took when it came loose and went through the rear fender. The caliper twisted all the way around the disc from it's normal position when it happened.



I kinda like the mag cover!
lol, thanks Nico.

I actually took it off today and broke the epoxy loose and reattached it. I saw in the pictures that the lettering was slightly off center so I reattached it so it's now straight. Sometimes it's not until you see things in pictures that you see things they way they actually are.
 

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Nice upgrades to make it yours Austen! I like the cover and the muffler! Need video for sound now! ;)
 
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Discussion Starter · #38 · (Edited)
Thanks Eric, I will. I'm pretty curious to see what it's putting out in terms of decibels now at idle so I'll turn the i-Phone decibel app on and get an estimate. I'm guessing it's gotta be around 100 decibels at idle.

Got the cap centered.... it was bugging the heck out of me seeing the lettering slightly off center in those photos.



Here's a couple of pics that Ellis sent me of the machining. Below is a quote from his as well.

This one was pretty straightforward.......as to the magnesium cover. Chucked it up on the ID, added some coolant, and put a .160" wide parting tool to it at 350 rpm's. Cap dropped like an egg into the nest.

The plastic version was chucked on the ID, but due to the amount of flex the part had, it had to be done gently. Actually turned the RPM's up to 500 to go for a freer cut, but dialed the feed rate down to a couple thousandths for rev. When I got it almost through, I unchucked it and finished the parting by hand with a deburring tool.

 

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Discussion Starter · #39 ·
Here's a short video of it running, Eric.

I turned the i-Phone decibel app on, shot it at the bike got, and got a max reading of 96 and a peak of 95 decibels on each fire while idling. The engine is cold when I took this so it's a little more smoky than when it's warmed up. The distance of each pop you see out of the exhaust gives you an idea of the compression.

 

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:popcorn: Popcorn's done. Tastes a little smokey for some reason. :D

I would have never noticed the lettering being off. Stuff comes out of the factories like that at times and would not have thought anything about it until it was mentioned. :coolpics:
 
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