If you feel like you have a deja-moo, well go back quite a few pages. Now I agree with all of you, who think that flatslides are the way forward, but on my Everyday TR1 practicality has its place too. And as I had to do an install from scratch, I thought I might as well document it. But if you're only here for the jetting and setup of the carb itself (stock settings in brackets unless, I didn't change anything):
Mikuni VM38-9 jetting & setup
- Pilot: 20 (30)
- Main: 175 (330)
- Air-screw 0.5 turns from a soft seat
- Needle: 6DP01, 3rd/middle notch
- Needle Jet: Q2
- Slide cut out: 2.5mm
- No Air jet
- two VM38-9 carbs,
- two VM38-200 inlet rubbers,
-
two 90 degree silicone reducer bends 57 and 64mm on their respective ends
(that is if you want to suck through the frame and stock airbox like me),
- a 2in1 throttle cable for VM36/38 available from various XS650 shops (#51-6506),
- choke-knobs as fitted to TM38s (not strictly necessary, but makes it easier to pull them out),
- two 40 degree throttle cable adjusters and
- four (4) M5x16 allen head bolts and spring washers per carb for a total of eight (8).
The latter not being strictly necessary, but it's a lot nicer to have some nice hardware on your carbs. The stock philipps bolts are actually JIS-heads, which means it's very hard to get screwdrivers in Europe that have the correct angle and not tend to slip out.
Optional
- you can also get a softer throttle spring (VM34/55),
- longer straight throttle adjusters (VM30/77) and
- a Mikuni Hex-mainjet jet tool if you think, you will have to change jets often. (This will allow you to swap mainjets with the carbs installed very easily.)
-
The lower half of an Yamaha XS or SR left handle-bar switch, if you want to
remove the choke lever in the most clean way possible. One can also just
simply unbolt the lever on the stock switch cluser.
Installation
Take the float chamber off and swap mains and pilots for the sizes of choice (in
my case 20 and 175). Add a bit of copper-slip or other anti-seize of choice to
the new bolts (after you put on the spring washers) and reinstall the float
chamber.
Swap out the lever choke (the lever is on the wrong side) for the knobs as they are easier to reach and more comfortable. The stock ones are usable though.
Yes, the TM38 chokes are a bit too long and will not go down all the way. Installation may also be easier with the knob pulled upwards.
Now the next step is, where things get a bit tricky. In the past, these 40 degree bends resulted in the perfect slack in the throttle cable, but either the cable I used when assembling the carbs for the pictures, has been shortened by me before (quite possible, as it wasn't in the original bag) or the other ones are slightly longer, either way they ended up being too short by a few mm. In case you want to go with straight adjusters there's longer (straight) ones available with Mikuni part-no. VM30/77, as the pre-installed ones are too short not allowing you to set the cable slack tight enough, which will ultimately lead to breaking the single cable.
On the subject of how to get it all back together, i.e. how to install the spring and hook the cable into the slide, that's how I do it.
And then finally install the lot. As you can see, the 40 degree bend would be nicer as it routes cable in a wider bend, decreasing the forces substantially as it avoids that last kink. Now if I absolutely wanted to make it happen, shortening the sleeve of the single cable by 20mm or so should give me ample room for adjustments, probably even 10mm being more than sufficient.
Now being a stubborn b*st*rd has its merrits, especially if if ends in "I-want-those-40-degree-bends-and-even-if-it-kills-me". If you leave out the locknut, the cables are just long enough then.
With that sorted, my old parts stash was raided for a suitable lefthand switch cluster lower, which comes without the choke lever. As they absolutely identical, it's just a case of not losing any bolts and swapping bits over.
The original TR1 lower.
And then the last bit was to properly sync the carbs both at idle and at midrange.
So that's taken me longer to write down than to install, which was roughly 45
minutes to one hour all in all. Does it require a sync? Well thanks for
asking, but if you check the cable lengths of the twin cables and they are the
same, all you have to do is set the adjusters on the carb tops to the same
height and that'll be good enough for a first start. Mine idled a bit higher
than I like and the airscrew was out a bit too far, but after filling the
float bowls up with some fuel, she fired right up.
As I had to revisited this post anyway let me recommend some further reading from this blog, some of which I wrote much later:
You can use stock intake boots and frame to carb elbows?
ReplyDeleteNo, you VM38-200 inlet rubbers and the carb elbows come from a turbo shop and are 90 degree reducers. I think 54mm (or 57?) on the frame and 63mm on the carb.
DeleteThey are 64-to-57mm elbows - just to make sure this has been noted down.
DeleteThanks, this post helps me a lot.
ReplyDeleteDidn't the idle speed screws of the carbs hit each other when the carbs are installed?
No, the idle-speed adjusters are on the outside. You can see it below the pink breather tube in one of the pictures above.
Delete