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Old 05-09-2013, 12:50 PM   #16
freetors
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Location: Collinsville, OK
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Hi, I really like your build idea! I've thought about someday building something with a similar concept. As a mechanical engineering student I am very interested in seeing your plans come together. You made it sound like you might be fabricating many of your own components like controls, parts, etc, is this correct? If so, are you going to be designing the entire bike and all of its parts as an assembly, or designing and building one portion at a time?

Good luck! I'll be checking back on this one!
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Old 05-11-2013, 06:32 AM   #17
XCgeek OP
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I decided on a Honda XR 100 engine as the power plant. This engine was chosen for a number of reasons including:
• Small. The 100 is considerably smaller in size than most if not all of the 150cc – 200cc options.
• Performance parts availability. There are heaps of hot up parts for this little engine including big bore kit, 6 speed transmissions, twin cam heads.
• Air cooled. No need for a radiator.
• 4 Stroke. No need for mixing gas.
• Available brand new or (as in my case) 17 years old with very little changes.
I looked around on eBay but didn’t see much that I liked. Most cost more than I wanted to pay. Because I always intended to use a Kitaco 145 big bore kit, I did not need an engine that was perfect.
Finally, through a post that I put up, I found what I was looking for. A 1995 XR100 that has been beat to within an inch of its life!

No photos of the frame but here is the engine, remove from the frame so I could create a rough CAD model.





I fully disassembled the motor. The oil screen was full of grass seed.



Most of what I wanted to keep looks good but I am amazed the motor ran long enough to wear the ring gap to almost 3mm!

The cases look like they have 15 years of oil build up on them.













So I send the off for cleaning to bloke that does vapor blasting on the side. They come back looking like new.





I remember years ago when my neighbor had a VFR750 which had these gold coloured cam covers. I loved them so I decided to paint mine gold also. I also painted the left and right engine case covers the same gold.



Love the cam cover colour but not sure on the side covers yet. They can be repainted if I don’t like them.

With the increased performance, I opted to put in a higher volume oil pump so I had to drill the oil port.



At some point in the engines life, the chain has come off and broken the left side engine case. Nothing structural but the case can not be sealed now so I will rebuild the case with JB Weld. Will this work or just fail after some heat cycles?

Next post: Lets make a frame

XCgeek screwed with this post 05-25-2013 at 04:53 AM
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Old 05-11-2013, 10:55 AM   #18
RedRaptor22
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Jb weld should hold up ok if you clean and rough everything nicely before you put it on.

I had an Xr100 as a kid and beat on it just like the one you ended up with, and most of that life was lived with Jb welded cases because of a snapped chain lol.

I think a case saver would be pretty much a must have on that engine.
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Old 05-21-2013, 06:45 AM   #19
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Got some more photos of the engine internals…both old and new.

I didn’t really have to look over the old top end because it is all going to be replaced anyway. However, it is a good indication of how the engine has been looked after and a great chance to see the difference between a standard engine for a AU$3500 bike and high performance components to release the potential of that engine.



Here are the basic items being replaced.



Check out the ring gap on the old upper compression ring! I measure it at 3.5mm. That’s more than 1/8th of an inch! I am guessing this bike was hard to start by the end.


Head looks ok. Lots of carbon buildup on the valves but not to bad.



Old piston looks ok to me. Minimal scrapes, no hot spots. Just worn rings?



Here is most of the new stuff that will be going in. Cylinder, head, piston, rings, crank, carb, clutch plates and springs, output shaft, kick starter shaft, gear selector shaft, cam chain, cam sprockets, cam, oil pump. I wont bore you with photos of all of that.

But here are some of the more interesting bits.



I like girls that wear short skirts and this new piston wears a short skirt.



Here you can see the difference in piston diameter. The crank also has a longer stroke to take capacity from 99cc to 145cc.



Not only does the new piston have a short skirt, it is not wearing panties! To get higher rpm, you have to reduce reciprocating mass.



The Kitaco conrod is beautifully polished



Nice new head with increased valve size and a new cam with increase valve overlap and duration.



I can’t wait to have a play with this new engine. I’ll have to find someone with a stock XR100 to compare.

I did not rebuild the engine straightaway cause I want to use the cases as a jig for the placement of the engine mounts on the frame. Once that is done, everything will be ready for the rebuild.

But! Talk is cheap and I I am here to build a bike, not reassemble an engine with some new bits. You are not reading this to see me buy some bits and make some pretty pictures in a CAD program of what the frame should look like. So lets hurry up and get into cutting some steel!

XCgeek screwed with this post 05-25-2013 at 04:58 AM
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Old 05-22-2013, 11:43 AM   #20
sailah
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Quote:
Originally Posted by XCgeek View Post
So lets hurry up and get into cutting some steel!


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Old 05-22-2013, 01:54 PM   #21
JagLite
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Talking small engines

One nice part of small engine bikes is that the parts are so much less expensive!
Imagine what those new parts would cost for a 450 or a 650.
Any frame design drawings you can post for us?
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Old 05-23-2013, 07:08 AM   #22
XCgeek OP
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Right, lets make a frame from scratch. I have probably bitten of more than I can chew here but I am a pretty stubborn so I will see if I can chew my way through this process.

I designed the frame to consist of ” tube with .035” wall with some ” tube tying the main members together.

I bought a heap of 4130 tubing, sundry solid bars and plate for the frame and some mild steel RHS for the jig



I needed to make a jig to hold the three important interface points in the correct locations. Head tube, shock upper mount and swing arm pivot point.





The jig also has some assembly aids to help confirm frame members are in the correct locations (but less accurately positioned than the other three items)

Several items in both the frame and the jig require turning. I was going to pay someone to do this for me but then I love buying tools so I bought a lathe. I don’t have a shed to put it in so I set it up at a friends place.



Here is my workspace. I’m not going to let the lack of a garage stop this build. (Although rain normally puts a damper on things)



So I turned up the frame components that needed turning. This is the first part that I messed up.



The head tube starts life with ” wall and finishes up with a 1.5mm wall except where the bearing races seat. My boring bar will only reach half way through the head tube so I have to do one half then the other. After finishing the first half, I then managed to make the bearing race to big. Doh! Start again. I will fix this one at a later date.

Now you can hate me. I didn’t take any other pics between here and the next ones. Sorry.

So, just like magic, a frame comes off of the jig.













I am somewhat happy with it. Made some mistakes that I can live with but my welding leaves a lot to be desired. I found it really difficult welding in and around all the tight confined spaces.

I have taken up a quick welding class to see if I can do better on the swing arm.

To make up for the lack of pics with the frame, I will take a few more of the swing arm.

Next post, a brake caliper mount.



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Old 05-23-2013, 07:19 AM   #23
XCgeek OP
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Originally Posted by Salsa View Post
Sounds like what I built a few years ago.

138cc Pitbike motor
Downhill Bicycle Forks
Bicycle rims
8" Double disk front brakes
8" Disk Rear brake
Fabricated bicycle hubs
Stainless Spokes
Adjustable Head angle
Competition Motocross Air shock (1)
Street Legal with License Plate
130 Pounds plus Gas

So then I wanted one that was more suited for offroad.

160cc YX160 Pitbike motor
KX85 Forks
17" & 19" Alloy rims
8" Double disk front brakes
8" Disk Rear brake
Fabricated bicycle type hubs
Stainless Spokes
Adjustable Head angle
Competition Motocross Air shock - Under Seat
Street Legal with License Plate
A little heavier - forks, rims, tires

Don
Hey Don,

With your adjustable head angle, what angle did you end up with? What is the range of adjustment? Did you try many different settings? Did the different angles make more or less difference than you thought it would?
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Old 05-23-2013, 07:59 AM   #24
JagLite
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Thumb Framed

The frame looks great!
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Old 05-23-2013, 09:42 AM   #25
Salsa
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Quote:
Originally Posted by XCgeek View Post
Hey Don,

With your adjustable head angle, what angle did you end up with? What is the range of adjustment? Did you try many different settings? Did the different angles make more or less difference than you thought it would?
I have been a 25 degree guy for some time. I haven't done many tests of angle, but I did accidently do one. I was in a race in Idaho with my 1975 350/400 Honda and I adjusted the head angle to somewhat less than I used for the California desert. During the race it slipped to full chopper. It was hard to turn.

Not being an expurt (pun intended), I am not as sensitive to the changes as I would be on a short paved track.

I would suggest 2-3 degrees on each side of what you think you expect to be right. How much you can put in depends on the design you use.

My design was a pivot at the bottom of the head crown and a slot at the top. I used a bolt adjustment to provide support to keep the angle from increasing (over jumps). An insert in the headcrown would be more rigid, but provide less adjustment.

Good luck

Don
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Old 05-23-2013, 11:24 AM   #26
Turbo Ghost
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How well did everything stay straight after the welding? Are you going to have the frame stress-relieved or go with it as is?
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Old 05-23-2013, 12:15 PM   #27
Te Hopo
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Super cool idea, I'll be following this one
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Old 05-23-2013, 03:05 PM   #28
XCgeek OP
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Quote:
Originally Posted by Salsa View Post
I have been a 25 degree guy for some time. I haven't done many tests of angle, but I did accidently do one. I was in a race in Idaho with my 1975 350/400 Honda and I adjusted the head angle to somewhat less than I used for the California desert. During the race it slipped to full chopper. It was hard to turn.

Not being an expurt (pun intended), I am not as sensitive to the changes as I would be on a short paved track.

I would suggest 2-3 degrees on each side of what you think you expect to be right. How much you can put in depends on the design you use.

My design was a pivot at the bottom of the head crown and a slot at the top. I used a bolt adjustment to provide support to keep the angle from increasing (over jumps). An insert in the headcrown would be more rigid, but provide less adjustment.

Good luck

Don
Thanks Don. My frame, as you can see, is not designed to be adjustable within the frame and without adjusting any other variable. I can move my forks up and down in the tripple clamps and I ensured that the bike is designed with the forks in the middle of that adjustment so that gives about a degree either way
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Old 05-23-2013, 03:10 PM   #29
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Originally Posted by Turbo Ghost View Post
How well did everything stay straight after the welding? Are you going to have the frame stress-relieved or go with it as is?
It all stayed pretty good but 90% of the welding was done on the jig. I had to weld in the cross bracing after I removed the jig and that ment I had to open up the swinarm mounts and hold them open while i welded the bracing in. It still clossed up a couple off mm though so I will have to make an allowance in the swing arm
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Old 05-24-2013, 03:03 AM   #30
andyhol
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whats the weight of the frame?
Great work with the reveal btw
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