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2 into 1 Intake crossover

Discussion in 'The Garage' started by bearcat, Apr 28, 2013.

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  1. Bob Kelly III

    Bob Kelly III Ranch Kid from way back,.... that got Old !

    Hi Griz Your talking about "Tuned Intakes " are you not ? I'm talking about "throttle Response" it's not the same thing just closely related is all.
    Bob....
     
  2. barncat

    barncat XS650 Addict

    I've started on the intake, will post a few pics when finished. It'll also appear later on my "hodaka tank cafe build" thread where I'll report on tuning and performance.

    Grizld1- thanks for the jetting tip. I must be badly mistaken; in searching online a while ago the leanest NJ i found for TM's is the Q series in 389 style? Plus this carb must use 7 series needles i believe... did i miss something? Were there different versions of the TM? Have a couple used ones that i thoroughly cleaned...
     
  3. grizld1

    grizld1 Grumpy old man Top Contributor

    Series 389 needle jets go all the way down to O-0 in size. Try Sudco or Carb Parts Warehouse. The generic needle for the TM34 is 5FP17; Jack could give you some good advice on needle choice, he has those carbs on his BMW twin; send him a PM. There's a good thread on tuning the TM34 over at XS650 Garage USA. I can't recall offhand what needle was recommended, but you can probably find the thread; if not let me know and I'll look it up for you.

    Edit: The thread is by member timg at www.xs650temp.proboards.com and it's "sticky noted" in the Fuel and Carb section, easy to find. Timg had success with the 6F9, the same thing that works for VM34 and 36.
     
    Last edited: Jul 10, 2017
  4. grizld1

    grizld1 Grumpy old man Top Contributor

    There were indeed different versions of the TM carburetor--TMX 2-stroke pumper (not made in 34 mm.), TM33/8012 and TM36/68 4-stroke pumpers, and a fine 34 mm. 4-stroke pumper that the bean counters at Mikuni America don't import. But AFAIK there was only one version of the TM34 sold as an aftermarket carb in the USA.
     
  5. barncat

    barncat XS650 Addict

    10-4. Thanks for all the suggestions, will do some more jet shopping. I'm pretty familiar with VM tuning but got off track on the TM jet choices.

    Will be curious to see how this carb/intake setup works. Still have to wire the whole thing and do custom foot controls etc so it's a ways out...
     
  6. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    EDIT Just forget this post the forum software is like facebook anymore it didn't show me about 3/4 of the thread til AFTER I posted up this makes no sense mess!

    no flow master I but I don't see a 1/4 tube moving enough air to make a difference in short manifold branches. Did you try a deflector? If you could make it thin and attach to the back of the wye it could be bent to adjust, then finish welded when you are happy. That carb seems really big... I hear lectrons described as barely controlled fuel leaks and as on off switches. i have box full of them but have never tried one. Maybe try a VM34 or 36mm see what it does, most places I have read say one cylinder or two doesn't change the carb size needed. Maybe try increasing the intake length by adding a sleeve between carb and manifold see if that changes anything.
     
    Last edited: Jul 10, 2017
  7. barncat

    barncat XS650 Addict

    Did easily find a 389 P-6 NJ on eBay so that's on its way.

    This carb uses 7 series needles so i don't see any way around that. They're 10mm longer than 6 series. Fattest leanest one i can find is 7F7. There is a 7F8 available but i can't find dimensions for it anywhere- perhaps others are better at search than i am...

    I see that there are two chopper style 1 into 2 manifolds commonly available that use 10-12" tracts, so not much question that this similar length U shape will work.
     
    Last edited: Jul 11, 2017
  8. grizld1

    grizld1 Grumpy old man Top Contributor

    Longest generic needles shown for any TM series carb (excluding pumpers) is Series 6. One of two things is going on with your TM34. Either it's a weird orphan carb (I have a couple of odd TM34/8012 type sets with odd design features) or somebody dropped in whatever was on hand. BTW the centimeter size designations for needles are approximate. Read series 6, for example, as "in the range of 6 cm."
     
  9. I have never had any 2 into 1 setup work on my 74 when i had it. Shitty idle and gas pooling. Single vm34. Pulled hard and everything above idle was great. Unequal lengths dont work. Tried joe wiseguy and another manifold. The longer runner never really got hot either. Poor atomization. If you could get it hotter. May have helped.

    If you could center it. Itd be worth the try though!
     
  10. grizld1

    grizld1 Grumpy old man Top Contributor

    +1, CDN--long runners and tight radius bends don't help atomization even a little bit! To center the carb you'd either have to cut out the backbone of the frame and convert it to a double cradle or put the carb behind the backbone, and then you'd be right back to the problem of overlength runners, tight bends, and fuel condensing out of the A/F mix.
     
  11. Aftet seeing how poorly my slant 6 runs in my valiant without the manifold heater im all for the heat. Haha
     
  12. barncat

    barncat XS650 Addict

    May well be an oddball carb. Think it was from an RM125. If the needle is too short it'll pull out of the jet. Will recheck but pretty sure it's 7series only.

    Tracts will be symmetric. Willing to bet it'll run well hot. Did roughen internal surfaces. No sharp bends.
     
  13. barncat

    barncat XS650 Addict

    Will finish up the intake tomorrow. Have final grinding/shaping on the plenum to do before welding. It's been a pretty exacting process. Have a novel idea about heating the intake that i may try if it needs it pending testing...
     

    Attached Files:

  14. Bob Kelly III

    Bob Kelly III Ranch Kid from way back,.... that got Old !

    OOOH heat the intake with the exhaust !!!!! ..... that would be hard to do but wouldn't be a drain on the battery as an electric heater would be !
    .... of course you could get into running the engine on vaporized gasoline too.... intake air needs to be over 110 degrees though to keep the vapor from immediately recondensing.... but people in the past have done it and got Huge MPG gains..... Most I ever got was 80mpg out of my ford pinto.... without heated air..... but I've been working on vaporization sense the 1980's ! LOL
    ...... and WOW you do nice work !
    Bob........
     
  15. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Any provision to manage vibration?
     
  16. Bob Kelly III

    Bob Kelly III Ranch Kid from way back,.... that got Old !

    good point 2M... that carb will have to be supported by a bracket to the frame I bet ..... sense it puts the weight of the carb back such a long way..... but that intake looks like it'll work to me ! it should deliver equil fuel to each side ! .....
    .....
    Bob..........
     
  17. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Well, I just see the carb dangling out there, shaking fuel like a margarita mixer...
     
  18. barncat

    barncat XS650 Addict

    Bob- you certainly zeroed in on my concept to heat the intake. Anyone who's ever touched a header knows how incredibly hot they get- fast. Maybe some heavy gauge bare coppper wire.........

    2M- I'm not overly concerned re vibration-yet- tho you're right to bring that up with these motors. This is 1.5" x .062 wall tube- weldment is very strong and rigid. TM carbs are also about the lightest out there. It's 6.125" from the head to inside of tube radius which barely clears the frame backbone, perhaps not as long as it looks.

    I'll post another pic or two here later but will then probably move this discussion over to my "Hodaka tank cafe build" thread for testing. This project has strayed from OP heading.
     
  19. Bob Kelly III

    Bob Kelly III Ranch Kid from way back,.... that got Old !

    You know, 2M has a point and he knows these engines better than anyone here I think .... perhaps a rubber hose mounting of the carb and have the carb base bolted to the frame ?
    I've seen vibrations turn carbs into junk before.... My brother in laws 305 scrambler back in the day was so heavy in the vibration department
    that it broke the frame destroyed the carb floats several times ( they were brass luckily so we resoldered them) , it got to the point that the emulsifier tubes would fall out ..... the main jets would wind up in the bottom of the float bowl and we'ed have to fix it on the highway, and in general made it Hurt to ride,.... the Buzz put your butt to sleep in a few miles,..... but it had twice the HP my 305 dream had ! LOL
    ......
    Bob.......
     
  20. barncat

    barncat XS650 Addict

    Fear not, will deal with vibes if and when it becomes an issue.

    Fini. I've got about 12 pretty intense hours into the manifold so it's time for an IPA or two... hope this thing works. Ported it post -weld and then blasted it internally with frac sand.

    Will do any follow up comments then moving this discussion to the aforementioned thread for anyone interested.
     

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