Motorized Bike Project.

[Megadan]

I got my bottom end back together and was able to check the squish gaps with the pistons I have on hand. I measured the chamber CC as best as I could and came up with a 6 cc chamber. Not exact since it is a fixed head cylinder, but fairly close.

Surprisingly, with both base gaskets in place the MS380 piston actually clears. It has a fairly tight squish gap of .6mm and would give a compression ratio of nearly 12:1, which is a tad high lol. The bigger issue is it blocks the transfer ports and closes off the exhaust port, so it definitely needs to be milled down to work.

The stock piston with both base gaskets has a 1.72mm squish gap and has an incredibly low compression ratio, 8.9-9:1. Possibly a design choice to keep heat down and allow it to run on cheap gas. With one base gasket it drops the squish gap closer to something more acceptable of 1.12mm, and bumps the compression up to 10:1 With no base gasket it's right on the edge of squish gap tolerance at .52mm, but like the 038 piston the compression is near 12:1

Unsurprisingly, the MS460 piston ends up with the best overall figures. With 2 base gaskets its still nothing special with 1.6mm squish and 9.1:1 compression, but with one it has a squish gap of exactly 1mm and a compression ratio of 10.45:1. A pop up piston with 2 base gaskets lands somewhere in the middle with a 9.6:1 compression ratio while also maintaining the port timing of the 2 gaskets.

I am going to run a flat top 460 piston with 1 base gasket as I view it as the best combination overall. and then likely port the exhaust side to restore some of the lost timing and increase duration.

[JerryHawk250]

Dangit Dan! Stop it! I don't need any more projects. Building these motorized bikes are so much fun. I got too many irons in the fire. I promise I'm not going to do another motorized bike. Not right away anyway.

[Megadan]

Originally Posted by JerryHawk250

Dangit Dan! Stop it! I don't need any more projects. Building these motorized bikes are so much fun. I got too many irons in the fire. I promise I'm not going to do another motorized bike. Not right away anyway.

LOL. Jerry, this is keeping me from having too many irons in the fire. I keep wanting to buy another motorcycle, but it's the last thing I need. This gives me something to fill the time and scratch the itch.


The funny thing is, this engine is considered one of the most powerful out of the box engines and here I am trying to improve it.

[JerryHawk250]

Originally Posted by Megadan

LOL.
The funny thing is, this engine is considered one of the most powerful out of the box engines and here I am trying to improve it.

You and I know there's no such thing as being the most powerful already.

[Megadan]

Originally Posted by JerryHawk250

You and I know there's no such thing as being the most powerful already.

Or that anything made in China isn't going to need some help to actually make it good or reliable.

[wheelbender6]

They have a racing league in California, but it is dominated by bigger four stroke mills.

[willardnigma]

anything over 40 on a bike feels, well "fun".

Saying from experience when I got mine to top out at 55 with just the right gearing (took a full mile to hit that speed).

Then the drain screw vibrated out and I lost my gas.

[Megadan]

Originally Posted by willardnigma

anything over 40 on a bike feels, well "fun".

Saying from experience when I got mine to top out at 55 with just the right gearing (took a full mile to hit that speed).

Then the drain screw vibrated out and I lost my gas.

I am more concerned with pulling power than top speed. With a 40 tooth rear my max speed at 9000rpm will be around 40 to 45. That puts my cruising speed around 20 to 35, which is all I desire.

[willardnigma]

Well you have the high compression setup. If you want more pulling power I'd lengthen the intake a bit, remove the baffle from the exhaust (if using the standard chinese 2 stroke one) and open it very slightly using a step bit.

and by slightly, I'd make it just 4-5mm larger than it's current opening diameter



Shorter intake and more open exhaust is higher rpm but less pulling power and vise versa.

The intake expansion chambers (boost bottles) have felt like snake oil to me. I haven't seen any improvement from them, just a change in sound that some perceive to be an improvement.


If you're feeling brave you can run nitro to the intake. I will say it is fun, as long as you don't have to turn and there are no potholes.

They do work, but only for a short stent and it's risky

[Megadan]

Originally Posted by willardnigma

Well you have the high compression setup. If you want more pulling power I'd lengthen the intake a bit, remove the baffle from the exhaust (if using the standard chinese 2 stroke one) and open it very slightly using a step bit.

and by slightly, I'd make it just 4-5mm larger than it's current opening diameter



Shorter intake and more open exhaust is higher rpm but less pulling power and vise versa.

The intake expansion chambers (boost bottles) have felt like snake oil to me. I haven't seen any improvement from them, just a change in sound that some perceive to be an improvement.


If you're feeling brave you can run nitro to the intake. I will say it is fun, as long as you don't have to turn and there are no potholes.

They do work, but only for a short stent and it's risky

The Phantom 85 standard exhaust is actually already a lot bigger than the normal.china doll engines. 28mm inside diameter with a straight 19mm exit pipe. The exhaust port matches the pipe and is pretty darn big. The intake side has very aggressive port timing and a steep slope just like the saw it is based off of. With a Reed and windowed piston combined with the exhaust and really good exhaust timing and blowdown right out of the box this engine is pretty torquey as it is. All I have done is bump the compression a bit and port matched the intake to the Reed block. I will actually play with more aggressive stuff later.

Boost bottles aren't worth the time. I have no desire to run nitro or nitrous or any other silly stuff. Premium unleaded is fine by me.

[Megadan]

Made a video somewhat covering the bike and build.

[Megadan]

My slightly bigger disc brakes came in today. 160mm vs 203mm discs.



Not to worry, the front is getting the exact same brakes. The main reason for the huge rotors is for sprocket, chain, and caliper clearance. The chain on the 40 tooth is going to create a potential contact point with the calipers, but it will hopefully be just close enough.



I am still going to have to space the rotor out, but with the new style of dual pull calipers I have, that has to be done anyway since the new caliper positions the pads further out than the original unit. Thankfully, I have a lot of room to work with on the brake side, so I actually think this will work out rather well.



You can also see in that last picture how far the caliper sticks in toward the hub. The new calipers I bought are a dual pull style instead of the single that the original units are, and as I mentioned previous the pad centerline is moved outward as well, but on top of that, they also stick inward less than the original units too.




So, my plan to to setup the bike and just start with the rear wheel and work my way forward. I plan to pull the rear wheel anyway to actually check the wheel bearings and make sure they have proper lubrication, it will be a good time to work on the rest of the setup. I just don't trust whomever assembled it.

The "OCC" sized sprocket hub adapter is sized perfectly for this bikes rear hub. My plan to hopefully prevent issues with slipping is to to key the surface of both the adapter and hub with a little sanding and then utilize some Loctite 638 retaining compound which has a shear strength over 4000psi and is also decently high temp and oil resistant. Thankfully this adapter is also machined properly and a nice snug fit with the hub, which will really help.

If you are thinking that the retaining compound won't be enough, I have watched that stuff hold a bearing race in place when the breaing locked on up an enormous 480V motor and ended up spinning the shaft on the inner race and wrecking it. It's some impressively strong stuff.

One nice thing about buying a cheap bike like this is my entire lack of guilt in buying cheap ebay parts to upgrade it. The parts on the bike are just as cheap and shitty

[Megadan]

I finally started to assemble my bike now that pretty much most of my parts have come in. I am still waiting on my dang handlebars but after 11 days of waiting they should be delivered tomorrow. That means I can get my controls and everything else sorted out next week.

In the meantime I went ahead and installed the motor so I could check sprocket alignment and get an idea of my hub adapter position. Fits in the frame rather well with decent clearance all around. Carb has enough room to install without having to unbolt anything, and I also think I can make my VM18 carb work with an angled foam filter on this reed block, which would be awesome.



I am currently waiting on some jets to use with this stock carburetor. I do believe they are a Keihin 99101-124 jets. I measured the one that came in the carburetor and the only real difference is it is .3mm longer. Otherwise they should install and function all the same. While the original jet is unmarked I did size it out to a 75, so I went ahead and ordered 78, 80, 82, and and 85. Many phantom owners complain of them being jetted on the lean side, and with the port matching and other work I have done I likely made it a little worse, so I wanted a decent range to work with.

In the meantime, I have another obstacle to overcome. My front tire and the exhaust are trying to be buddies. It's actually not too bad, so I should be able to fix this issue with a little torch and bend action.



My other obstacle is a little more frustrating, but I have to work within the parameters that I am given. It's the fitment of the disc brakes and sprocket/chain setup. Unfortunately, the 40 tooth, which I would love to run, is just a tad too big to clear the caliper. My attempts to space out the rotor created other issues and didn't buy enough room anyway.



My options here are 2. Both of them simple.

First option is to use a 36 tooth sprocket. This is the normal sprocket setup used on bikes with 26" rear wheels when using a 203mm rotor, so I know it will clear. The downside to this option is that it will gear me even taller, similar to a 32 tooth on a 26" bike. I don't mind if I have to pedal assist the bike a little, but it may prove too much gear. Lots of speed demons on the 26" bikes like using the 32 tooth with the Phantom. With an expansion chamber pipe and stock carb I have watched a guy do 52mph with no other work. Thats a little faster than I desire to go on a bicycle, but inversely, if the motor has the power it should cruise rather well at 30mph lol.

Second Option, if I decide the gearing is just too tall for what I want, is to get rid of the rear disc brake and go with a regular old rim brake out back. I will still have the bigger/better front brakes which is a plus. This would also allow me to pick almost any rear sprocket setup I want.

[Megadan]

Got my 36 tooth sprocket in and got it mounted up with the disc after servicing the rear wheel bearings. Kind of glad I checked them too because they were bone dry.

Honestly, it reminded me of the bearings the Hawk came with where they just had a little smear of that clear goop that they pass off as grease. Definitely going to check the front wheel and crank set now.

The other issue I stumbled into while working on the back wheel was I noticed one side of the axle is actually already bent a little bit. I'm just going to roll with it for now and look into some possible upgrade options in the meantime.

So, I am just going to install the rear wheel and check/tighten the spokes for now. If I can get those things done tonight I will get the bars and controls sorted out, then work on the exhaust. Supposed to be a rainy day tomorrow, so it will be perfect for some garage time.

My only other decision to make at this point is what size fuel tank to use. The half gallon tanks are nice because they are small. I bought a 4 liter tank, because why not? It's a bit big, but not obnoxiously so. I do like how it mounts better, with bolt-through tabs instead of the welded on studs like the small tank that are notorious for breaking off.

Hopefully I find this sprocket combo works out well because I really like how simple and clean it all went together. The caliper clears the chain perfectly and everything lines up just right. I took another note from my experience as a Chinarider and replaced pretty much most of the cheddar grade hardware that came with the hub adapter and on the hub itself for the brake rotor. They were already rounded out a little by whomever assembled the bike, so it was a good excuse.

[wheelbender6]

Lookin good! I would try to mount the engine so that the float bowl on the carb is level. Unfortunately, that will make the conflict between the exhaust and front tire even worse.