Some work on a TX650.

[Beazld]

Looking Good! You have a great eye for detail.
“Apparently, some business owners seem to think customers should be happy with sub standard parts???”
unfortunately to some places of business customers are a distraction rather than their sole reason for being.

[toglhot]

Well, the BS38 carbs finally gave in to their age, the diaphragms picking up little pin holes. I can get OEM slides with diaphragms at $140 a piece, but thought twice about that, vacuum carbs are just rubbish in my opinion. JBM in the US sell the diaphragms for $19, but, they aren't posting to Oz. So I decided on a set of Mikuni round slides - VMs. There are two kits, one kit just has the carbs and nothing else. The other kit, has manifolds, rubber boots, cables and a selection of main jets. I thought the more comprehensive kit would save me a bit of work, so shelled out $600 for the kit with manifold, boots and cables.

The carb kit arrived and so I bolted it on. Now, you'd think that a carb kit, put together expressly for the XS650 and costing $600 would fit without problems, don't I wish. I discovered the slide cable interferes with the fuel tap, so the carb has to be angled over quite a bit for it to fit. Totally unacceptable in my opinion. I discovered if I could fit the carbs to the original boots the cables would clear the taps, only problem was the carb spigots on the VMs are 40mm, whereas the boots are made for 47mm spigots.

So, two solutions, either turn up a sleeve and press it on to the VM spigot or spin up some new, longer ally manifolds. I didn't like the idea of modifying the carb spigots as they are a cast finish and would have required turning down first. So, I decided to make some new manifolds that would place the carbs 40mm further back, clearing the fuel tap. New problem, it would require a 90mm round lump of ally, turned down to 40mm for 60-70% of it's length, then turning out the centre to 34mm. A lot of waste there, so I decided to make the manifolds in two pieces, a flange to bolt to the inlets and a 40mm spigot 68mm long and press them together.

The flanges I made from 25mm stock, the spigots from 50mm round stock. Just turning the spigot down to 40mm and pressing it in place would result in scratching and gouging the spigot as it was pressed into place. So, I first turned up a lip 47mm x 5mm 47mm, followed by a 20mm section turned down to 40.2mm and the remaining 43mm down to 40mm to fit the rubber boots. Pressed it together and success it worked well. Of course I had to polish it before fitting. Good job, looks tops, clears the tap and gives access to the carb top adjuster for syncing. Now all I had to do was spin up an identical one for the other side.

That was today's effort, I spun up the spigot and flange and pressed them together, tomorrow I'll polish it and press in some brass spigots for attaching the manometer.

Longer inlet tracts result in torque being delivered lower in the rev range and a correspond lowering of power in the higher rev range., that of course would make the bike more usable in day to day riding. In reality, the difference in performance would be infinitesimal, only measurable on a dyno. Mods like this work well when in concert with other minor mods of the same type: Two into one exhausts, porting, Carb conversions and so on. The difference in inlet tract length on a stock bike to the new manifolds is less than 40mm, so even a dyno would be unlikely to pick up a difference.

[toglhot]

More of the same.

[Beazld]

Nice work!

[sid pileski]

I agree, beautiful work as always. Refreshing to see someone taking pride in what they are creating.

Thanks for showing what true craftsmanship is. It’s not about speed an quantity!

Sid

[oxford]

I agree, beautiful work as always. Refreshing to see someone taking pride in what they are creating.

Thanks for showing what true craftsmanship is. It’s not about speed an quantity!

Sid

+1.

Having screwed around with a few old bikes and doing similar work I can appreciate what you really have going on here.

[toglhot]

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.

[toglhot]

The carbs are normally supported at the rear by the airbox, but as this custom doesn't utilise an airbox, the carbs could possibly stretch and the rubber boots deteriorate. So, now I needed some sort of a support at the rear. So, I made up two U shaped brackets to fit over the slot at the back of the carbs, fitted them with rubber grommets and positive stop T nuts, then I made a larger flat bracket which bolts to the rubber mounted battery carrier and mounted the U shaped brackets to that, then anodised them.

Worked a treat and not too obtrusive or ugly. Next step, shorten the cables: I machined up a 6mm nipple and soldered that in place, then routed some fuel hose from taps to carbs. Another problem; The taps have a 6mm spigots, whereas the carbs have 8mm spigots. Back onto the lathe to turn up a couple of brass adapters.

All done, so I wheeled it outside, started it up and tuned it. Runs like a beauty now. But geez, what a lot of work!

[lbender]

But geez, what a lot of work!

Your command of understatement is only rivaled by your machining ability!!

[toglhot]

I made this this afternoon, total waste of time because this senile old fool made the slot too small. On the plus side, at least I know it's easily done and should look Ok in chunky, polished aluminium. Tomorrow I'll pay attention to what I'm doing and make one with the right size slot.

[Beazld]

To quote the late, great, and frequent contributor of this forum from the UK, Sir John, Earl of Sludgepump, “Clumsy Bastard!”😊

[toglhot]

I cheated, bent one up from 3mm stock. A lot harder to make this way and doesn't look as nice, but a lot less material wastage.

[oxford]

They look good, I think I like them better out of sheet anyways.

[toglhot]

I made a billet adjuster today so I could compare. I thing I prefer the billet adjuster.

[toglhot]

I finally had a win. Initially I made the adjuster with a 15mm slot to fit over the swingarm axle mounts. That didn't work too well, scratched the hell out of the paintwork. Next I tried putting a step in the slot, 15mm where the axle slips through and 16mm for the rest, but couldn't get a decent finish inside the slot. I know you can't see inside the slot when it's fitted, but, I know the finish isn't up to scratch. So today I milled the slot out to 16mm for the whole length, papered it reasonably smooth, then put it in the vice and stepped it by bending the ends in to around 15.5mm. Seems to work pretty well, so I'll try making another tomorrow the same way. I think I'm going to have to powder coat the frame though, the acrylic lacquer just scratches and chips too easily.