Newbie, intro and build thread.

[Jpvg]

Hi all just thought id join the site so various people can take a look at the recent XS400SE cafe racer that i have just completed. This was a barn find from Norfolk England which i have built to English road legal spec. Just wanted to say thank you for the use of this site it has been very useful and come in handy while going through the project. I hope you all like it as it was my first ever build. Being an engineer most of the parts where made by myself.

Dude this is a very neat looking bike! Amazing! I was wondering if you could maybe add a list of the parts you replaced? Trying to figure out which parts will fit on my bike and I like your idea!

 

[Peter B]

I have just joined the forum 2025 and saw this thread from 2016. I feel privileged to have acquired the bike that Stu Weyer built so beautifully back in 2013/14 posted on here first in 2016. I had pretty much given up road bikes. Had a number over the years including XS650's but until last week just had my KTM dirt bike remaining. I first noticed Stu's build for sale 2 years ago and was taken with the detail and craftsmanship - I was an apprentice toolmaker (albeit never did it for a living) and am now retired. In the past two years the bike has been sold three times - I bought it as I thought it wasn't being appreciated and I loved the evident quality of engineering and fabrication plus the overall look of the bike.

I've removed stickers, not to my taste, and cleaned it up a little - I believe it is still a beautiful bike and the quality of the fabrication and work done exceeded my expectations (I had to buy the bike blind it was located 300 miles away). It fires up nicely, on the button, I believe it has largely sat unused and so the carbs are going to need some fettling to get it to run right which I will do over the winter. I expect to enjoy riding this work of art on dry "high days and holidays" over Dartmoor in Devon UK for journeys of 20-80 miles max. A kick-start needed and a wee bit more fettling. Some other changes have been made in past 9 years but it remains an absolute credit to Stuart. ....spot the differences....

 

[CaptChrome]

Still a nice looking bike. Thanks for posting it as it is always nice to see these still going. This one is especially nice because I think Stu had a very good eye and spent some energy on the tail/seat mods. A lot of cafe bikes just look like the builder paid no attention to the lines and chopped the tail off making the bike all tits and no ass. This has great proportions and doesn't look too heavy up front.

Make it run good and ride it!

 

[Peter B]

Cheers CC. I will make it purr and ride it with a heart full of joy over the moor.

Have you any ideas other than Yambits of where to get Carb rebuild spares .... diaphragms notably as I'm struggling with the concept of paying +£60 for a small bit of rubber ...it seems somewhat usurious to me as an asking price but otherwise unobtanium creates distortions of value.

 

[CaptChrome]

any ideas other than Yambits of where to get Carb rebuild spares (Diaphragms notably)

Oooh, that question will lead you right down the rabbit hole. This is one of my favorite research projects!

For for Mikuni BS34 diaphragms there are only a few suppliers that I am aware of. I have not tried any of these personally, but if I were in need, these are the places I would investigate for availability, price and delivery time. Unfortunately, most of these sources, save one, are North America based, but perhaps someone in the UK is carrying this stuff as well.

http://jbmindustries.com/diaphragms.html

Also worth chasing down might be a distributor that handles K&L Supply Co. stuff. There looks to be some BS34 parts in the K&L catalog as they have a slide valve diaphragm part listed as 18-2805 3CF-14940-00-00 for the XS650 Std/Heritage Special/Special II 80-83 which uses the same BS34 carb as on the XS400, so it will probably work: https://www.klsupply.com/

I think Cruzinimage has the K&L part available for retail sale (also a bunch of other hard to find carb stuff): https://www.cruzinimage.net/2018/07/23/80-83-yamaha-xs650-carburetor-slide-piston-rubber-diaphragm/
This is a Japanese retail shop that definitely is worth a look. They might be the supplier for K&L.

Another big supplier used to be Sudco International, but I think they have discontinued operations: https://www.sudco.com/

As far as general carb soft goods for rebuilds, there is still a lot available directly from Yamaha, but I have good experience using kits from Keyster. These are made in Japan and I think are pretty good. I bought a basic kit from MikesXS.com here in the US. However, for something as important as butterfly shaft seals, I have only used the Yamaha OEM part as I think the quality is worth every penny of the cost (256-14997-00-00 or 2A2-14997-00-00).

 

[Peter B]

Thank you CC for your help and pointers very much appreciated. I will have time to do some due diligence later this week.

Tomorrow in the morning I'm going out on my 2002 KTM 400 dirt bike to enjoy Devon's green lanes after a long hot summer and two weeks of torrential rain should be interesting to see how they have evolved....

 

[Peter B]

Found this carb rebuild kit on Ebay in UK. Seems to be plenty of positive feedback reference the seller's other items and the kit price seems remarkably inexpensive compared to what I have seen being sought for the individual diaphragm's
https://www.ebay.co.uk/itm/35752036...lp:2332490&itmmeta=01K4X4B1RC954MBMTYNBGRJSBB

 

[CaptChrome]

I would not use the jets or the needle that the kit has. Clean and use your stock jets and needle or you may be asking for issues (at the very least don't pitch any hard parts into the trash before you really get to run the bike.) This kit also seems to have an accelerator pump diaphragm of some sort in there as well - I have no idea why as you won't find one in the carb. That is a red flag for me.

 

[Peter B]

Sage advice Capt C ref Indeed i will check out the quality of cheap stuff before ditching the original components. I suspect the photo of the carb kit maybe generic hence accel pump. Whilst awaiting the arrival of the cheap carb kit I just lifted the tank and seat off the bike and was very impressed with how the electrics were housed by Stuart. ...

However, I noticed something weird ... the R/H carburetor "inlet stub" / connecting manifold that is used to mount the carburetor to the cylinder has a very small diameter hollow rubber tube connecting to a spigot protruding from the inlet stub (manifold). The other end of the tube is not connected to anything. I blew down it to check it was not obstructed or blanked and found it it is clear i.e I could blow into the carb. I believe then this tube will suck air into the R/H cylinder when running .....and that would, I expect, cause running set up problems?! I cannot imagine what it is for or believe that this tube should be there? I can find no proper reference to it in my Haynes manual. There is a reference to a dust excluder on page 68 in Fig 2.4 Part 6 on top of the spigot (on both R/H and L/H inlet stubs) but no mention of spigot's use or of any hollow tube connection. I wonder if the spigot exists / is there to check carb vaccuum pressures? Perhaps somehow a tube has been left on the RH spigot rather than it being replaced by a sealing dust cap any insights would be appreciated if anyone has witnessed checking vacc pressures?

I have experimented by blocking and unblocking the tube with a screwdriver and it is defintely sucking air when unblocked. It runs better when blocked so I guess finding a dust cap next step.....

 

[tstidham]

Those are the vacuum ports. To be used for syncing the carbs and on bikes with a vacuum actuated petcock to run a line to the petcock. Usually it supplies vacuum from the right hand port and the left is just capped

 

[Peter B]

Ah I see thank you. so I need to know where it attaches onto the petcock. I will have a look in the daylight tomorrow appears to be a hose connection around the back of the Petcock I assume that's the place where the RH vacuum port hose connects into, albeit my Haynes manual has nothing clear about this hose connecting RH vacuum port and petcock at all. I imagine it hasn't been attached since I acquired the bike. I hope that's a big part of the reason the bike has been running so inconsistently (apart from starting which it does wonderfully) i.e the R/H cylinder would have been sucking air when it should not have been and presumably an inconsistent vacuum across the two carbs into the bargain as the engine got warmer ... which is when inconsistent running problem were most noticeable. Fingers crossed connecting hose to petcock - thanks for the advice

 

[Peter B]

Tstidham thanks are due to you too.

This morning I replaced the perished pipe from the RH vacuum port (the stub on the inlet cylinder manifold) to the Petcock. Just run the bike up in the garage from cold to warm (note weather here persistent precipitation presently - also known as pissing down - otherwise I'd go for ride). The throttle response is great - far better than to date, tickover settled at 1250 rpm (after a bit of fiddling).

I'm hoping to get out for a longer ride next few days after this storm goes through and that the carburetor spares kits I bought can remain on the shelf for the time being.... Cheers

 

[tstidham]

So you must have been running the petcock on the PRI (prime) setting to bypass the vacuum shut off. Now you can switch it to ON or RUN (I forget exactly) and let the engine vacuum turn the petcock on and off. Plus the RES (reserve) position will now also work should you have so much fun, you forget to stop for fuel in a timely manner and have to switch to it and head straight for a station for a refill.

 

[Peter B]

No Sir I wasn't using PRI position the Petcock was in the ON position. Despite my initial optimism about not sucking air through open ended vacuum tube which has indeed improved the throttle response - I subsequently had the engine cuts out when hot - fuel starvation seemed to kick in and engine died -In amongst everything else I made a schoolboy error ......ERRRR oooops having thought it over it seems I may have run the fuel out and needed to switch to reserve Doh! ...... I topped the fuel tank up this morning and tried it again today and seems all good even when hot. test ride out shortly when dry weather assured

 

[Peter B]

Currently the CV carbs performance seems to change with the wind and atmospheric pressure. I understand it is a common fault putting cone air filters. Flat sided Mikuni's or Kehlin...