TM34 Carb boot help

Moonmanzn

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Afternoon Gents
Hoping to get a link to a set of carbs boots that will take a 40mm TM34 Mikuni Carb. I have searched high and low and only coming up with 42mm ones for BS34.
Appreciate your advice
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That looks like the Topham Mikuni kit, so you probably already know that Topham (www.mikuni-topham.de) claims that OE boots for the BS34 carbs are tight enough. If you distrust that recommendation you might contact Sudco, the Mikuni America distributor; they'll have boots to fit your spigots and flanges. If you try the BS34 boots be sure they're Japanese made, and be sure to use the OE metal shrouds with them. I can tell you from experience that boots without the metal shrouds will crack at the ends of the spigot section unless you support these carbs at the back; they're heavy rascals. I love the TM36/68s, but I wish the bean counters at Mikuni America had seen fit to let us have the 34s over here; I'd already gone through the exercise of drilling, tapping, and joining AP reservoirs to run a single pump, drilling and tapping the blank bracket bosses, linking the throtttle shafts, and modifying the choke plungers for a rod-and-fork control before I found out that Topham offers the 34's with all of that work done. So it goes. Congrats on a fine choice of carbies. Component isolation is much tighter than in the old stuff, and you'll find the TM pumpers very easy to tune. You're gonna love 'em when they're done!
 
You don't state what model XS you have, and the answer depends on just that. At least the XS2 heads have parallel inlet flanges, so the carb boots have to be straight when using linked carbs, like those in the pic, or stock linked CV carbs. While the later, more common models have angled inlet flanges, and need carb boots with the corresponding angle to work with linked carbs. I believe you can get the correct 40 mm ID carb boots for the earlier head, but it may be more difficult for the later versions with angled inlet flanges.
 
Good catch! If memory serves (correct me if it doesn't, I may have confused you with another member) you also mounted TM34 pumpers on a late head. If so did you try BS34 boots?
 
Thank you for the replies gentleman.

Grizld - I bought these on a recommendation from you about a year ago...asked you what good carbs where and you told me these...they are fine bits of kit...I'm just struggling with the accelerator pump as I'm not a carb guru by stretch.

Articxs- my apologies it's a later xs big fin performance head. I was using the mikes pwk kit boots as they are 40mm but they broke after few weeks.

Twomanyxs- I have looked at your mentioned site but they don't seem to do one with 70mm between bolt holes and 40mm diameter.

I was going to try bs34 boots and take up the 2mm extra with some tape?

Your input is greatly appreciated.
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You might consult with Topham before trying to tape the spigots; it might not be necessary, and my gut feeling is that fuel vapors would eat up the tape in pretty short order. Defects of the XS Performance PWK knockoffs are well documented, but I haven't seen any complaints about the boots. As I mentioned above, the TM pumpers are heavy, and any boot that lacks the support of the OE metal shroud will fail at the spigot end. I found that out the hard way with a pair of JBM boots, which are very tough items--they failed right where the spigot section ends and the flange section begins. PWK boots may hold up for you if you support the carbs with a stiff spring or rubber damped bracket. Re. AP adjustment, I like the pump to actuate at around 1/8 throttle and stop at around 7/8. You might use that as a starting point, then experiment with adjustment to see what feels best to you. Just play with the AP adjusters a bit, you'll see how they work in a hurry.
 
Morning!

Thank You, I have the shrouds, might try bs34 boots, shroud and a clamp...then weld flat bar on down tube to meet up with carbs joining bracket and make small and tap a hole in flat bar and put small bolt in to hold up front of carbs to take the weight off. Ah ok the AP just has a actuator flap and adjuster screw. As throttle linkage turns the flap pushes down on pump rod and it squirts...so momentary pause then actuate through most of the turn and stop and the last bit of throttle?
 
If you have boots with shrouds they'll support the carbs just fine. Re. back support, if the BS34 boots won't clamp down tight enough to seal and you're forced to use rubber boots without the support of a shroud, don't hard mount the back support. The carbs need support, but they also need to be damped against vibration. Re. the AP, yep, you have the right idea. The plastic lever pushes the metal rod down, the metal rod pushes the AP piston down, and fuel squirts out the AP nozzles. The spring loaded screw sets the point at which the AP turns on, and the tiny stop screw sticking up through the carb top controls the shut-off point.
 
I couldn't see Topham's recommending something that won't work but I really don't like guessing, so I dug a VM34 carb body (40 mm. spigot OD) and an OE boot assembly (boot, shroud, and clamp) for the BS34 (42 mm. spigot OD) out of the stash for a test fit. Result: the OE assembly clamps down tight on the 40 mm. spigot. I wouldn't hesitate to use it.
 
Permatex variety of that self-fusing tape claims to withstand fuel, oil, etc. It is pretty cool stuff; I used it to rebundle some of those cloth wires down at the oily engine.
 
Hi,

Sorry to resurrect an old thread, but I am looking at the Topham TM34s for my XS2, also on Grizld's recommendation (I think you should approach Topham for royalties) and came across this thread. Artic you mention:
I believe you can get the correct 40 mm ID carb boots for the earlier head, but it may be more difficult for the later versions with angled inlet flanges

Do you have a link to the mentioned carb boots? Something like this?
 
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