Got a call from Roger. 11 days from now is the first and likely only dirt track race in our area. Afraid we're not going to make it. Probably best anyways, never ridden on a dirt track before:). I am stoked about getting this thing out there though. We'll post some video if I can get it sideways later. Hopefully we can keep it uprightish. Roger got his little Yamaha done. I don't have any good pictures, but I got one with my cell.
...back to the XS.
So some more progress.
Bottom end is mostly together.
Bought the 750 kit from Gary Hoos a few months back. Didn't bother sending him my cylinder as he had a '71 sitting on his bench. The only difference I could find was the four bolt tensioner vs. the six bolt on my "72, so I went ahead and bought it from him.
I welded a couple of lugs on to the tensioner mount so I could use all six bolts on my tensioner. I assume Yamaha did this change for a reason. Anyways now my '71 cylinder accepts my six bolt tensioner.
...back to the XS.
So some more progress.
Bottom end is mostly together.
Bought the 750 kit from Gary Hoos a few months back. Didn't bother sending him my cylinder as he had a '71 sitting on his bench. The only difference I could find was the four bolt tensioner vs. the six bolt on my "72, so I went ahead and bought it from him.
I welded a couple of lugs on to the tensioner mount so I could use all six bolts on my tensioner. I assume Yamaha did this change for a reason. Anyways now my '71 cylinder accepts my six bolt tensioner.
Got the cylinders on, then realized I forgot the o-rings for around the sleeve bottoms. So took it all apart and added the o-rings. It was then I realized when they bore the casting for the bigger sleeves, they don't bother with the o-ring grooves. So after some research... seems nobody bothers with them on the big bores, so off they came and the cylinder went back on. That was a waste of an hour or two.
New electricity maker installed. This is a nice piece. Don't hesitate to send $300.00 to TC Choppers, it's good stuff.
Don't like the kickstarter action so much. Has to rotate 70 -80 degrees before engaging. Have to open that back up and see if we can resolve this issue. Seems that most of them are like this.
Took out about 20 lbs. of shafts, gears and starter motor. We'll be kick only. Just as any good race bike should be. Have to figure out a good seal solution for the gaping hole where the starter used to reside. I'll get one of them nice lithium battery's from Ballistic, they're tiny little things.
Have to decide if we're going to put the stock decompression unit back in. The '72 has the cool little lever under the throttle, but of course this is gone with the modern throttle tube assembly. Have to figure that one out as well.
With all your engine mods I'm curious what pipe selection you would go with (ID, length, taper, reverse cone, etc.)
ReplyDeleteYour front end is very nice but if it was me I would swap right and left forks so that the caliper is on the underside of the left side's fork leg (easier on the handling and better weight distribution). Worry not about the brake line crossing over, it just means the tube then would be 'straighter' (milder bend), if you have length to spare that is.
Just my 02 cents! Good progress along!
Leon,
DeleteGoing to run a 1 5/8" 18 ga stainless pipe. Its going to be a high pipe on the left side of the bike. Likely run a SupertTrapp aluminum can with tuning disks.
As it is something I'm making, not all is decided yet. But I am going to try and get the pipe length around 26 - 28" with the muffler in the 13 -15" range. This will likely result in better low end power. Not looking for top speed here, much rather find big torque. This thing is going to be ridden hard and obnoxiously in town mostly.
Re: Brake.
Going to try it on the right side. Trying to pay a little respect to the Yamaha designers who mounted the caliper there in the first place. I like the fork leg mounted disc carrier so much, it's such a cool feature, I kind of wanted to try and capture the look.
We'll see how it functions up there. If I don't like it so much, I'll take your suggestion. I could flip the forks, flip the tire and be good to go. The only issue with flipping it is if for some reason the bearings ever seized they would try and unscrew the axle. Pretty sure the cotter pin would prevent disaster.
Anyways, thanks for the thought. I'd likely not have thought of it and sourced a new fork tube if I wanted to swap it.
Scott.
Hi Scott,
ReplyDelete26-28" primary sounds a little shy, which means this will concentrate on upper RPM, further supported by the choice of 1 5/8" diameter.
If you read (which I think you might have) the Performance Guide by Craig Weeks (the free downloadable sample is about his experience with pipes), most chose 28-31" pipe to begin with. I think 15" muffler is a good length though.
Thing is for stock xs650s, the exhaust port is already too large, which hurts exhaust velocity. But since your engine is 750cc with ported head, it should be a good match. However, rule of thumb is larger and shorter pipe will move power up the RPM, and smaller and longer will help low and mid-range.
Of course cam choice is also vital, but I think you already got this sorted.
Hi,
ReplyDeleteYeah I did read it. Most of those guys were running 1 3/4" pipes so that was part of my simple logic to go down to 1 5/8". We also put quite a bit of weld in the exhaust port, they have a much higher floor and are down to around 1 3/4" diameterish...
I'm also planning on a 2 into 1 collector before the exhaust can. I figured the back pressure created by that might justify the slightly shorter pipe.
Well thats my best guess logic anyways. I will consider the lengthier primary before we start welding.
Thanks.
Scott.
Hi Scott, I have a few cylinder head assemblies lying around that I need to find out their year. I have a good guess 2 of them are from XS2 (1972) but have no way of confirming.
ReplyDeleteIf it's not too much trouble, the next time you take photos could you take some extra detailed shots of the inner and outer sides of the top engine cover (the rocker box) so I can compare the castings between your model and mine?
Thanks in advance and please don't mind me if this is an inconvenience!
Hi Scott, a 1 53/64ths" freeze/welsh plug is the common blank used for the starter, used with some 3-bond sealant.
ReplyDeleteDoes Roger offer his porting services for xs650's..??
Regards,
Dale.
Thanks Dale. I ended up wit a Mikes XS "Starter Delete kit". Not certain I like the solution so much. Seems to pretty much clamp on the seal, not really retained properly. Anyways might do something with the stock cast starter end.
ReplyDeletePlan on racing a bit on the dirt, so I'm a little weary of the frost plug. Not likely, but could spit up a rock and nail it. Don't want to be the guy to dump oil all over the track :). I'm sure you are right and it'd be fine, just feel better with mechanical retention.
Thanks, Scott.
Dale,
ReplyDeleteSorry didn't respond to the Roger question.
He's not so interested in doing more XS work. He has sooo many projects on the go.
If you get a chance check out his website. He's done some pretty cool things over the years. Not sure if there is much up there on his current Boneville bike, but its amazing.
He'll be back again at the Bub trials this year with it. The bike has already run over 200mph, briefly. I expect he'll trash the existing record in his class this year... depending on the salt and all the other infinite variables.
Scott.