1974 XS/TX650 rebuild

[th62]

I've since discovered that JBM are not shipping to Australia at the moment. That leaves buying an OEM slide and diaphragm.. The cost for them is more than a round slide, so, I think I'll be going for a round slide kit. The kit cost more than a single round slide, but comes with a number of jets and manifolds. All I'll get if I wait until JBM are shipping again is two 47 year old carbs of a terrible design.

[th62]

have some VM round slides coming next week. I've read the cable interferes with the petcock, standard fare is to tilt the carbs inwards at the top to fix the problem, but, that's a bit too rough for my liking, so to circumvent the problem I made up these two 20mm spacers. Hopefully, these should move the carbs back enough so the cables clear the petcocks.

[asterix]

Ah, always a problem but to a problem, there is a solution. It is to us to find it!

[th62]

I bought some round slide VMs in kit form, they come with extra jets, cables , manifolds and rubber boots for mounting. The kit is put together as a kit expressly for the XS650. However, when I mounted them on the bike I found I had to tilt the carbs over quite a bit for the carb cables to clear the petcocks, amateur hour in my opinion. To stop the carbs hanging up on the petcocks, I turned up an aluminium manifold, 40mm longer than the kit manifolds . It moves the carb back behind the tap, so I can sit the carbs upright and get to the adjusters. Problem with is, the fuel spigot on the tap now gets in the way, so I swapped the taps left to right, right to left, so the spigot now faces forward. Rather than turn the manifold up from one 90mm round, solid lump, I turned the spigot up from a 50 mm piece, leaving a 2.5mm lip at the bottom. I used one of the spacers I turned up beforehand for the flange, enlarged the hole and forced the spigot through. The lip actually seals against the cylinder head stopping the spigot from shaking itself loose. Longer inlet tracts do move the torque curve further down the rev range, but like a lot of performance mods, twin carb conversions, porting, velocity stacks, and so, the difference in performance, particularly on a street bike, would be hard to pick up, only a dyno would pick up the difference. This was only a rough manifold to try it out, I'm happy with this solution, so I'll turn up two identical manifolds over the next few days. Once done, I'll polish the float chambers and screw tops and paint the bodies black to match the engine.

[steve1958]

Nice work and as the owner of a couple of XS650's I am always interested in new twists in their developement. I note that you have added an oil cooler as well which looks very neatly done.

[th62]

Yep, oil cooler and spin on oil filter conversion. I posted the build a few pages back.

[th62]

Finished off the right side manifold, looks OK when polished up. Unfortunately, you can see a couple of scraping from where I pressed the two pieces together, I'll try to fix that on the left side. I did make one boo boo with the flange, I drilled the mounting holes before the bore, bad mistake, makes it very difficult to line the three holes up. Oh well, I'm committed now as I've made two flange blanks the same way.

[th62]

So, finished machining the second manifold, managed to get the second one identical to the first, well not quite, the second one is 0.02mm longer, but i can live with that. i also turned up a couple of brass spigots, drilled the manifolds and pushed the spigots into place, then polished the second one and bolted them in place. you'll notice the spigots for the balance pipe is tucked up out of the way, bit of a bugger attaching syncing hoses to it, but i didn't want the balance tube seen. urned out quite good, the adjustment cable sits around 10mm behing the tap, so plenty of room to get a spanner in there for syncing. Outlet on the tap now faces forward so it's a bit of a trek to the carb inlets, and damn, the left side carb has the inlet on the same side as the right hand carb, so it's seen. so much for left and right hand carbs.

The carbs have to be supported at the rear via rubbers for vibration. I'll make a two piece polished ally clamp to clamp onto the main frame downtube and go from there.

[th62]

Finished off the rear carb mounts and anodised them. The brackets that attach to the carbs were brush finished prior to anodising, whereas the larger brackets was polished prior to anodising, so the finish is slightly different. Everything fits and works as intended, but it's very tight in there. The manifolds sit the carbs 10 mm behind the taps, so I had to swap the taps so the outlets faced forward. The small brackets attach to the larger bracket via a grommet and positive stop T nut, the larger bracket bolts to the front of the battery carrier which is rubber mounted. I also spun up a couple of brass 6mm to 8mm brash fuel line adapters.

[th62]

Wasted afternoon. Made the damn slot too small, this is what happens when you're old and senile. But, now I know it's easily done and should look Ok polished up, nice and chunky. I follow the measure once and make twice rule. Tomorrow I'll have another shot.