OMS Ironhead Thumper : 04

We have been pecking away at the tasks to get this Ozark Mountain Scramble Ironhead ready for June 2014. Here in Western New York the riding season stops at the end of October so shop time is not interrupted by the desire to ride in sub-freezing temps until April.

The Rear spring struts were not doing it for me for the overall look of this bike. The rear sat too low and the front is too high. I found a pair of stock 13-3/8” long XL883 rear shocks in my stash that I removed from my wife’s new Sporty back in 1997. These brand new shocks have been in a box in my attic for the last 16 years. I figured this project was the perfect candidate to use these forgotten gems. So, off with the struts and on with the shocks. I like the look better than the struts on this bike but they are really soft and with my fat ass on the bike the springs compress farther than I would like. I guess we will be adding pre-load spacers to the springs to carry the extra load and keep the sag to a manageable level. We will post more on that procedure in the future.

The Ironhead motor will be losing half of its displacement when I remove the rear cylinder so we needed to give the motor a little help in the final gearing department. We installed a smaller countershaft sprocket for some extra mechanical leverage. We went from and 23/49 combination to a 19/49 combination. I pulled a few links form the existing chain so everything fits correctly. I hope this is enough to let this bike get out of its own way on the twisty mountain roads of Arkansas.

We decided to use the horseshoe style oil tank that came in the box of parts with the bike to keep costs down and mounting of the battery simple. The only problem is the original tank mounting system is flawed and parts are missing. I rigged the tank to mount from the original regulator/battery box iso mounts and reworked the original oil tank frame mount on the right side of the bike to hold that side and the third mount will have a custom bracket that ties the oil tank to the inner primary. I am hoping the iso mounts and the 4 point mounting configuration will be enough to hold the weight of the battery and 3 quarts of oil. This is all for now stay tuned for the next update for the rear tail section and foot controls.

Tim

tt500 build : part 11

When I got this bike running, it was clear the carb was having idle issues. This mixture screw was probably the main reason why. Stupid screw. I have no clue what bike it came off of, but it isn't the stock one.



Then there is this plastic liner thing. It almost looks stock right?



Nope. That is a drywall screw anchor thingy. I don't know the technical name, but that's what it is.



The threads in the carb body were a bit galled, so I chased them with a tap and put the new mixture screw kit in. If this doesn't fix the problem, I'm going to push the bike in a lake. Maybe. I'm sure the wheel bearings will lock up when I try to move it into the murky water.



Now on to the front brakes. In a search for simplicity, I decided to find a bolt on caliper for the tx750 forks. Apparently the body for these were used for a handful of different Yamaha bikes of the era. From the xs650 to the rd350, the bodies are the same, and with a quick hardware swap can be moved from one side to the other depending on application. On top of that, the rear calipers on some models were the same.Yay?



Unfortunately the front calipers usually run a flared fitting with a short hard line, while the rears run banjo. I don't want the extra connections, and prefer just a more common banjo fitting with a single line. A little light reading told me that the flare fitting will pop out after threading a screw through it. Sounds simple enough.



With a gentle tug, it popped right out. Ready for banjo duty.



Since this project seems to be a never ending car crash, it's fitting to find out my current xs650 rotor is the wrong one. The offset on the later model bikes were different than the early ones. The early 2 piece will fit my setup, but the one piece won't. Dammit. That's where I'm stuck. If anyone out there has one they will let go of, shoot an email to hatchethairy@yahoo.com and hopefully we can work out a deal. It looks like this.