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Author Topic: 1983 XV500 Cafe Racer  (Read 38913 times)

Offline brad black

  • Posts: 132
Re: 1983 XV500 Cafe Racer
« Reply #190 on: Jun 30, 2017, 22:02:12 »
buy the kjs manifold.  it'll work much better, and as cxman says, a lot of the better will be low speed stuff.

that black manifold looks like it would function quite poorly to me.

Offline Grazz256

  • Posts: 167
Re: 1983 XV500 Cafe Racer
« Reply #191 on: Jul 01, 2017, 09:47:17 »
Strictly from an air flow perspective...
The airstream can't make sharp turns, so you are going to get some dead areas in the flow.
For the bottom corner that projects into the air stream you are going to have a high velocity area right on the corner and spirally inversions/dead air on the side closer to the cylinder. For the top corner you will have dead air in the corner.
The higher the velocity through the tube the more these areas will grow and the smaller the effective cross section of the tube.

This might help visualize what is happening..


I didn't actually watch that video so I have no idea what it is actually about, so just take it as a pretty picture (unless its an interesting video, then I will take credit  ;))

Someone else can chime in on fuel droplets and such, I'm just the airflow guy..

Offline Karlloss

  • Posts: 207
Re: 1983 XV500 Cafe Racer
« Reply #192 on: Jul 05, 2017, 13:45:36 »
Put some finishing touches to the top yolk. The reason it's taken so long is the need to purchase the right tool for the job, in this case a 2mm slit saw.

They say a bad workman blames his tools, very true, but you still need the right tool for the job.






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Offline brad black

  • Posts: 132
Re: 1983 XV500 Cafe Racer
« Reply #193 on: Jul 08, 2017, 10:41:37 »
i would put a pinch bolt for the centre stem too, that way you don't need to load the top nut to secure the yoke.

Offline jagtmans

  • Posts: 8
Re: 1983 XV500 Cafe Racer
« Reply #194 on: Jul 13, 2017, 19:33:21 »
It's taken some time but the manifold is ready and the carb mounted on the bike. When I got the bike it would hardly start (you could say it wouldn't start) and the 2 times I got it running it died after a few seconds. I had not expected it to run with the new single carb setup, and of course it didn't... ;) Then I followed some good advice from different forums and changed the spark plugs. That actually did the trick!

I haven't changed anything to the carb yet, so I put it on as I got it, with a 45 pilot and 165 main jet. I adjusted the idle and just turned out the fuel mixture screw 1 turn because it seemed to be running a little better that way. The AP isn't working so I have to fix that because I have the "bog issue" when I open the throttle fast. But when I somewhat gently open the throttle the bike actually responds pretty well. Even though the spark plugs look OK, I do have the feeling the bike could use a little richer mixture. But that's something I have to fix by setting up the carb correctly. But at least it starts and runs idle steady, and responds to the throttle so I'm happy for now.

Like I said the manifold is glued together. The glue doesn't take temperatures over 100 degrees celsius (I tested that by heating a piece of glued aluminium with a blow torch). So using glue to attach flanges to the manifold to bolt onto the cylinders was out of the question, as the outside of the cylinders will get hotter than that. And taking cxman's comment on the too sharp edges of my first design into consideration, that made me redesign the manifold and use the stock intake boots. By turning them around they face eachother at an angle of 20 degrees. So now I only had to make "sharp" edges at an angle of 10 degrees each, which I smoothed out on the inside as best as possible. the rest of the downward angle into the cylinder is now taken care of by the boots which are rounded on the inside so should make airfow much smoother than with the sharp edges. Added bonus is that I now have a thermal insulator between the cylinder and the manifold, which prevents the manifold from getting too hot and breaking the glued connections. Besides that the rubber boots also take up some vibrations and give a little room to play in case the manifold isn't "spot on" sized. All in all this manifold has cost me less than € 30,- in materials and tools I had to buy, and it actually seems to be working. So I'm quite happy :D

Anyway, I've put up a short clip on youtube of the bike running. You can see it here:

And yes, I know I should have put on an air filter but I haven't got that yet and was eager to test the carb setup ;)

In the movie you also see the mounted KTM front fork, which was more or less a bolt on solution with the pyramid parts bearing replacement set (both top and bottom 48x30mm). The wheels will be replaced by spoked ones which I already have. Front will be and 18" (which is roughly the same outside diameter as this 90x90x19, so both engine and ground clearance don't seem to be issues) and rear the standard 15" for now at least. I managed to get hold of a 535 rear wheel that included the drum brake at a bargain. The only problem with that wheel is that you can't mount it in the rear fork without taking the final drive off, because it's like 0,5 cm too wide to slide it in. And mouting the drum brake when the wheel is already on the final drive doesn't work either. But that's something I'll have to figure out or learn to live with. It's not a lot of work unbolting the finl drive and I hardly ever take out the rear wheel anyway...

Here are some pics of the manifold:
« Last Edit: Jul 13, 2017, 19:57:44 by jagtmans »

Offline Karlloss

  • Posts: 207
1983 XV500 Cafe Racer
« Reply #195 on: Jul 23, 2017, 06:43:59 »
Good work on the manifold, certainly given me food for thought on which way to go.

I wasn't aware the 535 hub was slightly wider, I'm interested to know why it won't slide in, is it the spline drive being slightly wider or something similar?  If so could it be machined down a tad?

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« Last Edit: Jul 23, 2017, 06:49:06 by Karlloss »

Offline Karlloss

  • Posts: 207
Re: 1983 XV500 Cafe Racer
« Reply #196 on: Aug 11, 2017, 13:20:43 »
Mounted a steering damper as I've set the rake at 24 degrees, I thought a steering damper would be a wise move.




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Offline ChopperCharles

  • Posts: 27
    • Modified Motorcycles by Chopper Charles
Re: 1983 XV500 Cafe Racer
« Reply #197 on: Aug 11, 2017, 13:47:46 »
Get a drop tree from Cognito moto. https://cognitomoto.com/collections/fork-conversion-parts/products/1-rise-triple-clamp-lower

That'll give you another inch.

Open the forks up and add a spacer to increase the length. You can probably add another inch this way, maybe as much as two.

Either machine some spacers to use the original wheel, or get a GSXR hub and lace up a larger front wheel with spokes (also from cognito moto). The GSXR forks on that Virago frame is going to increase trail significantly, because the offset is so much less. To counter that, you'll need to drop the front end and/or raise the rear. There's only so far you can raise the rear before the driveshaft starts binding (7 degrees deflection is the limit for reliability, you can go as high as 14 degrees but longevity of the driveshaft will be compromised)

Charles.

Offline Karlloss

  • Posts: 207
Re: 1983 XV500 Cafe Racer
« Reply #198 on: Aug 11, 2017, 14:39:15 »
I'm not using a Virago frame, I've made my own. The wheel in the picture isn't the one that'll be used, I have an 18inch to put on. I'm happy with the 24 degrees, I designed it that way.


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Offline ChopperCharles

  • Posts: 27
    • Modified Motorcycles by Chopper Charles
Re: 1983 XV500 Cafe Racer
« Reply #199 on: Aug 11, 2017, 14:42:11 »
Yeah, I see that now. I was replying to the first page info, and I see now that there are four pages :)

Nice looking build! I wish I had the machines you do! So jealous!

Charles.