The Raven

This engine is very sensitive to air temperature density, I tried the 75 and it really didn't like it, although in a matter of an hour the air temp dropped about 20 degrees and picked up a misty chill. I did a quick drag up and down the street and I knew it wasn't happy on the main jet so I limped it home at part throttle, which is out of the main jet circuit. I think the 80 will be a good conservative jet to use, and maybe take the short e3 spark plug out and pop a NGK in there, in the 7-8 heat range, they seem to resist fouling better. I noticed on my BMX that I was able to jet the top end wayyy richer with a NGK than a e3 spark plug and picked up about a pony and 1500 more revs. It's kind of a bummer, since the e3 is nice and short and prevents any stray arcs to the frame. Blah.

Oh wait, the e3 worked better on the BMX, now I'm kinda lost as to what plug to pick, OEM KTM is a NGK B8HS, which is a spark plug used on high compression high revving car engines, so its really long, and I was dealing with dielectric breakdown of plug caps to the frame. :/

Well I think I might have a convenient solution, I'm gonna try a e3.12 instead of the e3.10 that's in there, since I think maybe its actually too hot of a plug actually, the strap is just so dang fat that you can't read the color off it. The 3.12 is supposedly cooler, around a NGK 7-8 range, that should be better. I haven't found a short NGK that would be comparable, it must exist somewhere, it's very difficult to order spark plugs by desired specs rather than by application though. I think the 75 jet might work well with a cooler plug.

I took her out and ran down the road for a plug chop, and its just slightly on the rich side. This e3.12 plug works much better and I was able to get a good reading off of it showing its slightly rich (reddish brown), which the ride confirmed. Since its about 60F out, and it will be colder on average this winter during the day this setting should work well.

Some things I was remembered of from way back, you gotta warm the engine up completely before running, or the plug will wet foul. A plug with a skinnier strap would probably work better before fully warmed up, the E3's have split strap that doesn't run as hot, and it's cross referenced to 6-8 heat range plugs from other brands. I would consider it more of an 8, they claim the catalytic coating on the strap helps low temp self cleaning, but the real benefit of these plugs comes from reduced misfires from multiple arc paths, as it didn't skip a beat once hot. At the autoparts store they had a NGK equivalent to this plug, but it had shorter threads and wouldn't protude into the combustion chamber as far, the E3 goes the correct length into the chamber and wouldn't drop the compression a point or two, so I figured it's the way to go, and more closely matches the NGK BH8s recommended for these (which has a long body which doesn't fit the chopper well, and arcs through the cap).

Another thing to note about this type of carburetor is that it has four different circuits that control the fuel delivery through the powerband, and that if I pulled full throttle before getting to high speed, it went into the main jet which is too rich for mid-rpms. The proper way to ride with this Dellorto PHBG is to gradually twist the throttle so it transitions through the four different circuits with their respective jets. When I rode like that on the return run, the engine ran like a top, forgot how much of a buzz this thing gives you just from the amazing racing sound!

Edit: Mental note, 75 main jet with this plug.

with the 44t the top speed is 60+ mph, with pedaling required up to about 15 mph to get it going, not really recommended for sanity or safety's sake, but it rode nice and smooth at that speed and the hydraulic brakes are more than sufficient. I have the 80t on there and it currently maxes out a little over 45mph and accelerates without even pedaling, takes off with strong acceleration, you can hit top speed in about 8 seconds if you twist it just right. I can quote you on shipping when you're really serious, because I need to figure out how I'd pack it with the wheels off and the bars disconnected, and find out a final package size and weight.

Might want to look up the import laws for motorcycles from America, I can figure out shipping when you're ready. I expect it would cost at least 300 dollars to ship to SK, that's a rough guess, depends on carrier, level of deliver, and the final package or crate weight.

Yeah the pedals are functional, it is quite a pain to pedal though lol. One reason I changed the gearing to the 80t was because I needed to basically sprint on the cranks to get it up to about 15 mph before throttling up completely to take off with the 44t. The way it is now I just push off to get some balance and pedal up to 5 mph and take off, you can take off from a complete stop but its better on the clutch to give it a little head start. The red stone OEM clutch with diagonal gas grooves is actually very durable, even when I was slipping it a lot with the 44t it incurred minimal wear, and I changed the gearing to the 80t before it broke in with the clutch drum completely.

If there is any problems with this bike being a borderline motorcycle according to customs, the engine comes off with two bolts and I could ship it in a separate box. You might also look into the complete engine importation regulations, which should be at least better than US importation, I've ordered a pocket bike engine from Canada before, so I would think if they can get engines into Canada from China easier than into the US, then it might work in reverse.

I got bored tonight so I figured I'd take out the vinyl tape and stripe this new rear wheel to match the front.

So after ordering my third magneto since I've started riding this bike, I have decided to try and make them last longer, granted it's been an acceptable cost at $25 a pop, and I've ridden many miles, but the mag coils shorting out over time from heat is a systemic problem with KTM50's so I think there must be a simple solution.

Here's the mag stator with two coils, it sits inside a plastic cover, which I have drilled for venting at the front and around the periphery by the coils, it has helped some, but when a mag goes out it makes the bike run all weird, do crazy stuff, and bog under load or high rpms, altogether a pain experience because it makes you think something else is wrong.
I figure some fancy heat shielding should help to keep the stator cooler, heres the stuff we use to protect electronics and CF tubs on race cars at work, I was able to get a small scrap of it today for the mag.

I'm going to wrap the engine side of the stator with this, around the plastic potted coils completely, and maybe install it with nylon bolts vs the stainless ones on there, and use a ground strap. I'm also thinking the mag might last longer with a resistor inline with the kill switch circuit, to prevent the coils from flowing a lot of juice that would normally not flow continuously when charging the CDI and pushing it through a high resistance spark gap. I like to reve the bike and let it ovverrun to burn off the fuel and oil on the plug before shutting it down, and it may lead to too many amps going through the mag when doing so. The major killer is engine and clutch heat for these, as stated on KTM50 forum threads, but the current flowing through the coils can also generate internal resistive heating that eventually breaks down the enamel on the wires and causes the coils to lose inductance, which leads to loss of CDI charging capability.

It's worth a try anyways, and this gold heat shield is only $20 per square foot, so I might buy more in the future for other things like this. I'm thinking about probably putting some on the engine facing side of the CDI too, because it too contains inductor coils which can break down due to heat from the jug.

I wrapped my new magneto coil and my existing CDI and went out for a ride today. I can get all the revs again without it bogging or doing funny runaway revving crap, yayyy!



It's lunar lander meets motorbicycling, lol!

I had the piston ring stick again on the new clone piston on my last ride yesterday, so I think I'm going to go with a Namura or Vertex piston kit next, because they use coatings on the skirt and are available in exact fit sizing to prevent the piston tilting in the bore, which is what I think causes the skirt wear which makes the ring stick. They're undoubtedly made from better material and to closer tolerances, so it will be worth the extra $25 or so over a clone piston again. The cylinder is cast iron, and tough-as-nails so I'll just hone it to get the aluminum out and maybe hone it up a size for the new kit if it needs it for proper clearances.

I ordered up a Namura top end rebuild kit with the needle bearing and gaskets included in the kit.
Here's a picture of a similar kit for the liquid cooled engine.

I also ordered up a 1 5/8" 240 grit silicon carbide flex hone so I can hone the cylinder out to the proper clearance for the new kit. I'll probably do it on the drill press to ensure the best result.

My flex hone got backordered so long that I lost interest in the project since I was also busy with work. I'm going to try to get the new top end kit together in the next couple of weeks so I can ride the Raven again, and maybe put her up for sale. It's a tough choice but I would like to keep building new bikes and try different ideas. This bike certainly has the most Grand Prix feel to it, even more than my Motobike, since it has tons of grip and stability and the engine screams so sweet at crazy high rpms. I'm thinking about making a new build that's more utilitarian, maybe like a homemade Motoped or possibly an electric.