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Installing Jets and Relocating the Rear Head Breather

Discussion in 'How-To' started by slowrower, Mar 24, 2008.

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  1. slowrower

    slowrower 2007 Mastiff

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    After fiddling I finally got the right jet combo. Pretty easy task so follow along. Before we start if your bike is stock, most likely it is running lean to pass EPA and will need re-jetting even if you stick to the stock exhaust.

    [​IMG]

    Step 1 - Remove the aircleaner cover (ok mine is not stock but the stock)

    [​IMG]

    Step 2 - Cover is off, now remove the airfilter (mine looks a little squished)

    [​IMG]

    Step 3 - Now we need to get out our 1/2" socket and take out the bolts that hold the backing plate to the heads.

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    [​IMG]

    Step 4 - Remove the backing plate from the carb once you have the rear head breather hose removed from the backing plate. (were gonna dump this thing).

    [​IMG]

    Step 5 - VERY IMPORTANT ** SHUT THE FUEL OFF **

    [​IMG]

    Step 6 - Loosen the fuel line clamp and remove the fuel line from the Carb.

    [​IMG]

    Step 7 - Remove the fuel overflow line (small tube on the right side of the Carb.

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    Step 8 - Remove the four screws holding the fuel bowl to the Carb body (two in front , two towards the rear.

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    Step 9 - As you remove the bowl keep it level as it is filled with gas, once removed dump it into a suitable container. (how about that lawnmower)

    [​IMG]

    Here is the fuel bowl .. ok, next post!
     
  2. V

    V Guru

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    Question with the Doherty Power Pack backing plate will the bowl not drop with out moving the plate? I know it def. will not with the stock BD plate


    Thanks V
     
    #2 V, Mar 24, 2008
    Last edited: Mar 24, 2008
  3. slowrower

    slowrower 2007 Mastiff

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    Installing Jets and Relocating the Rear Head Breather - Part 2

    [​IMG]

    Here is the bottom of your carb with the fuel bowl removed. Your jets are in the middle and on the right side .. they look like (next photo)

    [​IMG]

    Starting from the left are your main jets 0.74 (stock) 0.76 and 0.78 -- on the right are the intermediate jets (under 2500 RPMs) the main jets kick in around 2500 rpms the 0.295 (stock) 0.31 0.33 --- I am using the .078 and .031 as this seems best for my altitude and exhaust (V&H 2-1 BR) - If it should stumble a bit below 2500 RPMs I will up the intermediate jet to .033 which should remove the stumble.

    You can drill out existing jet, just remember you enlarge it too much and your gonna have to get a new one. These came with the exhaust so no drilling for me -- otherwise I 'am a drilling!

    Step 10 - Using a short screwdriver remove the and install your new jets. On the fuel boat is a small line with a small rubber o-ring BE SURE THIS IS IN PLACE.

    [​IMG]

    Step 11 - Next, loctite the screws and re-install the fuel bowl - connect the fuel line and over flow line, backing plate, air cleaner and cover your DONE!!

    but ... theres more -- lets get rid of that ugly black rear-head breather line.

    First remove the clamp holding the breather hose to the one-way breather valve. You have a few options here, you can replace the short hose from the rear-breather valve to the carb's backing plate, replace both hoses (from the head to the valve and from the valve to the carb or like I did to the ground for now (I will install a dump can), or relocate the valve under the bike so just the SS hose is visible. I left the front hose on mine but again you can plug this as only one breather for the engine case is needed. For this you plug the head and the intake manifold.

    [​IMG]

    [​IMG]

    Remove the hose

    [​IMG]

    Install a 24" length of SS braided 3/8" hose and clamp it.

    [​IMG]

    Run the hose down the head and to the left of the carb

    [​IMG]

    Here mine is passing the Oil Pump on its way to the frame

    [​IMG]

    Next I will install a dump can (Puke Can) to prevent shit from getting on my scoot as it ages.
     
    #3 slowrower, Mar 24, 2008
    Last edited: Mar 25, 2008
    Chopper Dave likes this.
  4. barhopper

    barhopper Another round please

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    You may think about a puke can to dump into. You don't want oil spraying all over your bike. Its not much oil, but as you get more miles, it gets worse. Just my 2 cents.
     
  5. slowrower

    slowrower 2007 Mastiff

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    Installing Jets and Relocating the Rear Head Breather - Part 3

    [​IMG]

    Now remove the rear-head breather fitting from the backing plate


    [​IMG]

    Plug the breather hole


    [​IMG]

    Install the backing plate to the carb but do not tighten the bolts yet. Put the backing plate bolts in and make sure you have a good fit

    [​IMG]


    [​IMG]

    Install the air cleaner and cover and your done .. next time the front breather host and the rest of the rubber hose on the rear head breather.


    [​IMG]

    This is the stock backing plate I have starting re-working -- I removed all the burrs with a grinder and wet sanded it smooth (dam thing was a mess). For those not wanting to spend $$$ on a Doherty you can improve the stock one with some sandpaper and patience.
     
  6. slowrower

    slowrower 2007 Mastiff

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    I that is what will connect on the bottom of the hose .. dam thing hadn't arrived in time and I wanted to get things back together as its great riding weather. Good advice!!
     
  7. slowrower

    slowrower 2007 Mastiff

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    I am sure its possible but finding the screws, changing the jets will be much harder.
     
  8. Chopper Dave

    Chopper Dave SIICK!!!

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    looks good slow:up: but you can run that check valve at the bottom of the bike....and then do the front breather hose too....
    [​IMG]
    [​IMG]
     
  9. barhopper

    barhopper Another round please

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    Yep. It wont puke if motor is fresh, but it will eventually. Good job on your bike.
     
  10. lee

    lee Well-Known Member

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    good post slowrower - for those that don't know the jets on the left are the main jets which kick in at around 2500 - I would also recommend draining the carb before removing the float bowl
     
  11. slowrower

    slowrower 2007 Mastiff

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    Good idea chopperdave .. I may do that when I get some more hose. :2thumbs:
     
    Oscar Maldonado likes this.
  12. Oscar Maldonado

    Calendar Participant

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    Nice How-To slow!
     
  13. V

    V Guru

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    Nice work:2thumbs:

    V
     
  14. superfly

    superfly Ride it like you stole it

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    Slow, great how to. i ordered my new jets. We'll get together and do some more work on the sleds.
     
  15. haze324

    haze324 Active Member

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    Sweet How To. With so many guys swapping out pipes this is really handy.

    Can you explain the process a bit. I def. on a tight budget and have patience so any little thing I can do to improve my dog that I can do on my own I'm all up for. :up:
     
  16. slowrower

    slowrower 2007 Mastiff

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    Anytime .. get your tank mount? dam cold this week!!
     
  17. slowrower

    slowrower 2007 Mastiff

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    Hi Haze, the stock backing plate is rather ugly being made in a mould or mold. Under close inspection its pretty ruff which is not good for efficient air flow. The goal was to remove all the defects and polish all areas that will come in contact with air entering the engine - makes it look better too! As for improving performance with out a before and after on a dino can't say.
     
  18. Gas Man

    Gas Man Cool isn't cheap
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    Also... slow... why don't you flip that rear hose... and the vlv for proper alignment... so you have SS coming out of the head instead of the rubber.
     
  19. slowrower

    slowrower 2007 Mastiff

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    In my description I reverese the jets ... the main jet is 0.74 (Stock, 0.76 & 0.78 (I used the 0.78). The Intermediate Jet starts at 0.295 (Stock) 0.031 (I am using the 0.031) & 0.033.
     
  20. slowrower

    slowrower 2007 Mastiff

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    Good idea, working on that now .. it will be SS from the head to the frame where I will mount the value and a K&N breather filter. As it gets older (engine that is) I will add a puke can .. dam things are expensive.
     
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