Found a Sweet Engine, What Now?

[Techbiker]

After building HS 50cc, a HT 70 and a GT50R CAG bikes, I have decided that I am ready for something a bit more reliable, powerful, and comfortable (but still a motorized bike).

For me, these requirements mean finding an engine that includes true power generation abilities and is shift-able for comfortable mid-thirties cruising. I thought that a high performance 4-stroke would give me what I was looking for.

Anyway these previous engines had many upsides and drawbacks. The HS is quite reliable, however it has virtually no charging (for lights) or shifting options and power is not exciting. The Happy Time was reliable but so poorly built that horrible vibrations hurt long road-trip prospects. External charging options are better but still limited. Finally, the GT50R is incredible power-wise and is as smooth as silk. Unfortunately, no real external charging or shifting options exist. I also can't help destroying clutches on the GT50.

I spent a long time perusing Ebay and Alibaba for an engine without too much success. I almost settled on the CG125 engine, however I could only find a couple in the states due to overburdensome EPA regulations. I was also concerned that 125cc and around 11 hp would be too much for a bike frame. The smaller Honda clones are typically horizontal engines and may have trouble fitting almost any frame.

I called up motosport.com and they gave me a ton of very helpful engine suggestions. We decided that I should consider engines from small Enduro dirt bikes. After quite a bit of searching, I realized that the XR80 might be the perfect engine for my goals. With 110 watts of power generating capabilities, it can drive a fuel injection setup, a headlight and a tail light! This engine also has 5 close-ratio gears, a light crankshaft, kick-start, and a 9.7:1 compression ratio. Topping off the engine package is the fact that it produces ~5hp and weighs no more than ~45lbs. Finally, I have heard that the XR80 is incredibly reliable.

At 10.5" wide, the XR80 engine is narrower than my HS50 with Grubee 4G.

$315 netted me a clean real Honda XR80 engine with 180 psi compression! It should include a pre-wound stator to help charge a motorcycle headlight since I got it off an Enduro bike. The seller also gave me his Big Gun exhaust for only $80. Finally, I picked up a service manual, wiring harness, and carb.

Here's the rub though. I could not find information on the height of this engine online. It turns out that the motor is between 14" and 15" tall, probably due to the OHC design.

What should I do? Should I try to find/ modify a frame to fit this engine or should I try to source another type of engine? I do not mind adding a drop loop to a frame if it isn't too much money.

I feel like the Felt Bixby Cruiser is a close fit, however I do not have any specs on the space inside the frame. The benefit of the XR80 is that the jug does not look enormous (only 10cc larger than a HT 70).

Note that the engine mounts are in the front and rear of the engine. I should not have to support the engine from the bottom.

Thanks very much. Pictures attached.

 

[2door]

I'd build or modify a frame to fit the engine. Start with a good strong frame and either add a drop loop or modify the existing space.

But also concentrate some effort toward brakes, tires, rims and spokes. That's a lot of engine for a motorized bicycle but a much better option that some of the monster, big CC things that have been suggested here before.
Good luck and keep us posted on the build.

Tom

 

[wret]

You need to make one of these!

 

[Techbiker]

Engine Comparison Pics!

Hey guys, thanks for the information! I think that I will try to find/modify/build a frame to fit this engine. I'm definitely investing in quality wheels and brakes as well. The wheels will have 11/12 gauge spokes. I will keep everyone informed on this build.

Maybe this engine will become a nice option for motorbikers who would like a bit more power and comfort?

Wret, what frame is that? Are there plans that I can purchase/download? It looks sweet!



Here are some better comparison pictures that should give a better idea of the size of this engine. It isn't much larger than a HS50 with 4G transmission in any way except for height. I bet that the HS50 with mount and transmission is greater than 30 lbs as well. Note that the red bike with the HS50 uses a 19" frame.

P.S. The oil left in the engine is light colored so I am hopeful it was well cared for.

 

[wret]

The rear triangle is a Worksman.

Here's the plan:

 

[MotorBicycleRacing]

Re: Engine Comparison Pics!

Hey guys, thanks for the information! I think that I will try to find/modify/build a frame to fit this engine. I'm definitely investing in quality wheels and brakes as well. The wheels will have 11/12 gauge spokes. I will keep everyone informed on this build.

Maybe this engine will become a nice option for motorbikers who would like a bit more power and comfort?

Wret, what frame is that? Are there plans that I can purchase/download? It looks sweet!

Check out Silver State Cycles board track frame which has a big drop loop.

They also have some very heavy duty wheels with a drum front.

 

[Techbiker]

An Update and Info on the XR80 Engine

Thanks for the suggestions!

I checked out Silver State Cycles's website, and was intrigued. After speaking with Scott a couple times, I mailed off the engine! I'm keeping my fingers crossed that no problems pop up. Wret, I was going to submit your plan to a local frame builder but I doubt I could beat Silver Cycle's prices.

Scott thinks that the can get this to fit in his frame, albeit possibly with some massaging. I'm definitely getting a fuel tank and jack-shaft from him as well. The only issues are sorting out the rear brake and shifter setup. We'll see how it turns out.

Should I look into fabbing up a foot brake for the rear wheel?

Anyway, I will post pictures when I get the frame and engine back!

I'm planning to call my friend at DFW Powercoating http://www.dfwpowdercoating.com/ to schedule coating for the frame.

P.S. for those interested in the XR80 engine. I spent time comparing parts lists for the XR80 and XR70 (an engine similar to some of the horizontal Chinese atv pit-bike engines). It turns out that the XR80 uses a 14mm thick kick start shaft. Compared to the pit bike engines, this thing is massive.

The XR80 transmission is supposedly very nice and seems beefier than the XR70s. Even the XR80 stator is 15 watts more powerful. The crankcase is the same width as the XR70 and pit bit crank cases. Interestingly, the engine is at most 15-16" tall, compared to 17.7" long pit bike engines.

Finally, a gentleman who installed a 95cc hop-up kit got over 8hp from the XR80. I've heard that 10hp is achievable. This should be an interesting project!

 

[wret]

I'm still up in the air over the rear brake arrangement on mine. I may fab up a foot brake but currently I'm thinking of looking for a stubby handlebar lever for the clutch and keeping the rear brake on the right bar.

 

[CTripps]

I'm still up in the air over the rear brake arrangement on mine. I may fab up a foot brake but currently I'm thinking of looking for a stubby handlebar lever for the clutch and keeping the rear brake on the right bar.

Grab a dual brake lever and set up both brakes on it.. They're no more than $10-$12. Most bike shops have them if you ask, or order online (and wait for it to come). I've done it on each of my builds with no problems or complaints.

 

[Techbiker]

Grab a dual brake lever and set up both brakes on it.. They're no more than $10-$12. Most bike shops have them if you ask, or order online (and wait for it to come). I've done it on each of my builds with no problems or complaints.

Do you have any experience with dual hydraulic setups? I've been considering plumbing front and rear hydraulic disc calipers into one lever assembly or purchasing a dual blade lever.

 

[wret]

Grab a dual brake lever and set up both brakes on it.. They're no more than $10-$12. Most bike shops have them if you ask, or order online (and wait for it to come). I've done it on each of my builds with no problems or complaints.

That's a great idea! I kicked this around before but was a little concerned that the force required to engage two sets of brakes with one lever might be excessive. I'm going to look into a dual cable kit. I really want to keep my brass levers if I can.

 

[CTripps]

Do you have any experience with dual hydraulic setups? I've been considering plumbing front and rear hydraulic disc calipers into one lever assembly or purchasing a dual blade lever.

The only hydraulic brake experience I have is from working on my car, so not a lot of help there.. I honestly hadn't even thought of hydraulics on a bike build.. interesting idea, it could work out.

That's a great idea! I kicked this around before but was a little concerned that the force required to engage two sets of brakes with one lever might be excessive. I'm going to look into a dual cable kit. I really want to keep my brass levers if I can.

I've used dual levers on my builds since about a week or two after my first one was done. I just found my handlebars too crowded with a clutch lever and both brakes, and I had a little trouble with the 'overlap' of the clutch and brake lever on the left side. The lack of real estate on my beast's bars doesn't help either....

(...and there's a phone holder not shown mounted on there as well now...)

 

[Mungface78]

I'm very intrigued, subscribed!

 

[maniac57]

Here's some info and ideas...
http://www.ebay.com/sch/i.html?_nkw...id=10232&keyword=dual+pull+brake+lever&crdt=0


http://motorbicycling.com/showthread.php?t=10950

 

[silverbear]

Looks like an interesting project and a good engine choice.
SB

 

[Techbiker]

Those cable-driven dual brake levers are so tempting at around $15. I have nearly-new front and rear Stroker Trail hydraulic brakes so I hesitate to move "back" to a mechanical disc setup though.

Have you heard of daisy-chaining the front and rear hydraulic calipers together? Theoretically, this makes using one hydraulic lever easy.

By the way, do you have any front fork recommendations? I had the struts on my car custom-valved to my preferences so I understand the importance of good suspension damping. Do you think independently adjustable compression and rebound force is important for this build?

Is it worth "springing" for this fork?:

http://www.chainreactioncycles.com/us/en/rockshox-argyle-rc-coil-forks-20mm-2014/rp-prod85103

Unfortunately, I doubt that a classic "springer" fork is sufficient for 30mph+ cruising.

Also an update:

I discovered that the XR80 carburetor has low and high speed jets. Not wanting to spill gas on myself over and over again while trying to hit the perfect jet combo, I chose to go another direction.

I purchased the Ecotrons Small Engine EFI kit! Hopefully there won't be any re-jetting, choking, etc. in my future. The company claims to provide free tuning support. In fact, they recommend sending in your logs for in-house tuning. I will let you know how it works out.

 

[maniac57]

I have very little experience with bicycle hydraulic brakes, but I have heard of ''daisy chaining'' two calipers to one piston. I think it would work.
You might need to use a larger piston lever to actuate two calipers since you are effectively halving the application pressure by splitting between both wheels.
Mixing a big lever with small calipers should be workable if a stock setup does not work well.

 

[Techbiker]

Maniac,

Finding a large enough master cylinder piston is one of the big problems with a dual caliper setup. I found some for large motorcycles, however these levers are often expensive. I don't even know if they will mount to bicycle handlebars.

I think I have decided to swap brake levers so that the front is on the right. That way, I will have easy access to the most important brake. Then, if I do not like having a clutch and brake in the same spot, I will fab up a thumb brake for the rear. It's easy enough to do with a right lever flipped upside down.

I also picked up a XR100 clutch assembly. It turns out that the xr-100 uses 4 clutch pads and 3 plates in its clutch basket versus 3/2 on the XR80. I'm not sure if I need the upgrade, but it means the clutch should last longer! I'm excited about slipping this clutch as much as I want since replacement clutch sets are around $40!

Thanks for the helpful comments.

 

[FFV8]

Techbiker:

Let me help you a little with the brake issue. I am running a hydraulic disc on the front of the sidehack:

What you want is a scooter brake Master cylinder & calipers.

You do not want a larger master cylinder. Keeping the smaller master gives you more total braking force. Going larger would reduce available braking.

With the scooter front caliper in that picture, you get a pressure limiter. It is the cylinder hanging on the front of the caliper that the hose is attached to. The scooter folks call it "Anti-Lock". It is adjustable, and this is what you would use to proportion your front-to-rear braking force from a single lever.

With that single lever and front caliper I can stop that heavy bike from 30 mph with one finger. The pressure limiter can be adjusted to skid the front wheel - or not.

I chose the brakes with the plan to add a rear caliper if I felt it was necessary. The lever travels about 1/2" at the tip of the lever from rest to full braking. Adding a second caliper might increase the total travel 25%, but would make the braked that much easier to modulate.

Adding a second caliper to the system would require a longer banjo bolt for the master cylinder, something that should not be too hard to find.

By using a pair of calipers with pressure limiters you should be able to balance the braking system. The scooter parts are more robust than bicycle parts, and the single front caliper will stop a 700 pound scooter from 40 mph tothe limits of the tire.

Hope that helps

 

[Techbiker]

FFV8,

Thanks a bunch for the help! I ordered two of the GY6 50cc front calipers (apparently the one you ordered). I was going to get the dual piston ones from a 150cc scooter, however I realized that you are running a single piston caliper.

Do you currently only have a front brake?

Also, what rotor are you using with your front scooter caliper? A regular bicycle one? It seems that the hub holes on the scooter rotors are too big to re-drill.

Thanks again

 

[FFV8]

Yes, I have only the front brake. I was planning a rear, but have not felt I needed it.

The Big Wheel has a 2 piston caliper, on a 300mm rotor. It is a heavy machine, and the little caliper will lock the 19" motorcycle tire if you use more than two fingers on the lever:

When I put the sidehack together, I was concerned that I was going down to a 180mm brake disc, so I planned for a rear brake. I found a 180mm rotor I thought was a bicycle rotor:

But it was about 1mm thicker, and as you can see I had to re-drill the 6 bolt pattern. If you look at the pad marks on it, I think some of the bicycle rotors might work. As long as the braking surface is mostly round. Bike parts tend to be thin - the spandex crowd worries about grams.

I looked around on e-bay, and found the same rotor I used. Apparently it was used on some sort of scooter:

Scooter brake rotor

while not a direct bolt on, it is beefier than the Avid G2 Rotor, and about the same price.

I know there are some 290mm bike rotors out there, and that would work too. I had to remove a little forging flash from the caliper to clear the spokes - a larger diameter rotor would move the caliper away from the spokes.

.