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New to bikes, engine running poorly.

Discussion in 'XJ Technical Chat' started by Carrot feud, Jul 13, 2022.

  1. Carrot feud

    Carrot feud New Member

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    Hello, I'm new here and new to motorcycling. Recently came into possession of an 85' 750 maxim-x (canada) figured it would be a fun project to learn on. I'm an electrical technician on a wind farm, so while I'm not completely clueless, carberated engines are not my forté.

    I managed to get the bike running, after doing some minor things. The bike starts easy and idles fine. If I leave the choke engaged it will eventually ramp up to a high idle of around 4k rpm, as I understand that is normal. While in the high idle, the bike sounds great, and runs smooth. However if I remove the choke, and try to apply any throttle the bike sounds terrible, almost like its misfiring, and will sometimes even stall out at 2kish.

    How can it run smooth at 4k with choke but sounds like it wants to die with a little throttle? One of the needle jets clogged?
     
    Last edited: Jul 13, 2022
  2. Jake750

    Jake750 Member

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    The problem might be your religion. May I humbly invite you to join the church of clean?
     
  3. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The choke (actually an enricher) is a seperate set of fuel passages that supplements the idle mixture. If the idle jets or passages are dirty or clogged that will be masked when the choke is applied.

    While this is not a guarenteed fix for your problem, a simple and relatively inexpensive first step for someone who has never worked on a carburetor is to buy a can of Seafoam and follow the directions on the bottle for adding it to the gasoline. If the idle jets are flowing at least some fuel the Seafoam will gradually clean the crud out. You should notice a difference after the first tankful of fuel if not before.

    While you're doing that, hae a good read.
    The Information Overload Hour
     
  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Not yet. But eventually.

    OP, this is what Jake750 is talking about
    IN THE CHURCH OF CLEAN
     
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  5. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    An alternative to Seafoam is Berryman's B-12 Chemtool : https://www.berrymanproducts.com/pr...-carburetor-fuel-system-and-injector-cleaner/
    Seafoam has be difficult to find in my area lately.

    Just to quickly elaborate on what @k-moe is saying:

    The carbs on these bikes have three circuits - three paths by which fuel/air can make it to the engine. There is the enrichment (a.k.a. "choke") circuit, the pilot circuit, and the main circuit.
    Enrichment circuit - manually controlled by the "choke" lever. This circuit is used to enrichen (add more fuel) to the mixture to make starting and running a cold engine easier.
    Pilot circuit - This the primary source for low-RPM fuel/air supply.
    Main circuit - This kicks in at higher RPMs.

    So if the pilot circuit is clogged or otherwise not working correctly, then that can be masked by the enrichment circuit providing the extra fuel that the pilot circuit is *supposed* to be providing. Which sounds like what you are describing.

    There is also an adjustment on the pilot circuit to adjust the fuel/air mixture (rich/lean). If the pilot adjustment was severely lean, then that would be just like having clogged pilot jets.
     
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  6. Jake750

    Jake750 Member

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    I am suspicious that Berryman's Chemtool is what fried my carb diaphragms
     
  7. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    How did you get fuel up onto the diaphragms??
     
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  8. Jake750

    Jake750 Member

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    I am not sure. I just assumed that some atomized gas would find its way up to the diaphragms. The diaphragms were probably bad before but they were absolutely FUBAR after.
     
  9. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    I can't imagine any type of solvent being real good for the diaphragms....
     
  10. Jake750

    Jake750 Member

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    I typed that weird. What I meant was that I assume some the atomized gas found its way to the diaphragms somehow.
     
  11. Carrot feud

    Carrot feud New Member

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    Wow, thanks everyone, I'll start reading. I noticed some rust in the bottom of the fuel tank, so I have it set aside for now until I figure out what to do there, and I'll run some seafoam and gas through the bike with a temporary setup and see what happens.
    I guess I didnt think about the idle jets because it seemed to idle fine without choke. But between those or the pilot jets makes sense as it really isnt happy between 1-3k.

    I should definitely learn more before I get too deep.
     
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  12. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Was there a fuel filter installed?

    [​IMG]
     
  13. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Neither can happen.
     
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  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Add an inline fuel filter as insurance. It may be that rust and crud is what got into the pilot jets, but usually that also clogs up the enrichment jets as well.
    HOW TO: Install a fuel filter

    @chacal is out go-to for parts, but a fuel filter is pretty easy to get locally. make sure that it looks like the one pictured in the thread. There are metal bodied filters of that size (which I prefer) available on Ebay and Alibaba, but shipping usually takes a few weeks. The plastic ones work just fine though. Make sure to inspect it every year as they can deteriorate.
     
    Last edited: Jul 13, 2022
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  15. Carrot feud

    Carrot feud New Member

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    So, it had a fuel filter on, just one of those small flat ones youd see on a lawnmower. I replaced it yesterday with another small crappy one as that's all they had at my local store, but I do plan on putting a better one on eventually.
    I just pulled the spark plugs out of curiosity and 3 of 4 look really good, no gunk or discoloration. The 4th was much lighter, looking at a reference chart I'd say it was too hot. Would it be safe to assume the correspondong carberator would be the one having clogging issues, running too lean and getting hot? Or would that be a seperate more chronic issue as the bike has only ran for 10 min in the last year.
     
  16. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    THAT is the most likely source of the problem, and at the very least is making any other issue worse. Paper filters, especially the flat kind that are meant for lawnmowers, do not flow enough fuel to keep the fuel level in the float bowls where they need to be when under load.

    Photos of the plugs would be helpful. Number them from 1-4, and place them on a neutral background.
     
  17. Carrot feud

    Carrot feud New Member

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    I did snap a pic of the bad one, will grab the rest next time though. Wouldnt a restrictive filter affect it with choke on as well though? 20220713_165612.jpg
    Sorry, I can take a better picture eventually as well
     
  18. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    That is super lean. Focus on that carb.
    A restrictive filter would make it run richer than intended. No filter (or a high-flow filter) would make it run leaner.
     
  19. Huntchuks

    Huntchuks Well-Known Member

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    Gap? Looks like the electrode post is worn away to the insulator. NG.
     
  20. Carrot feud

    Carrot feud New Member

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    Gap was ok, the bike had iridium plugs with the pointed electrode so it's hard to see in the picture.
    I'm changing the plugs and going to run 25% seafoam in it, then I'll check the plugs again after. If it's still rough I suppose I'll be learning more about the inside of the carb.
    Also, does anyone have an opinion on k&n air filters? The seal around this one is junk and I dont think I want to buy another, rather go closer to OEM.
     

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