1. Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

31A/33F to 58L

Discussion in 'XJ Modifications' started by cds1984, Dec 4, 2017.

  1. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Hi,
    I have just re-assembled my 33F engine after procuring some std 58L pistons from Germany and some OEM 58L std rings and getting my 33F barrels bored to suit.
    Head has valve seals replaced and valves lapped in freshly.
    I am putting a set of mikuni BSC36 carbs in but I have the original BSC35 carbs from the 33F so...
    You are now witness to this experiment.
    and yes... I just can't help it and can't help looking forward to the pain and suffering.

    Updates after I finish putting it back on the road... hopefully next week.
     
    skylrk62 and chacal like this.
  2. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Stepping backwards... only a bit though!
    Was hoping my sexy fully refurb'd 36mm carbs with new JBM diaphragms, etc etc would be okay but in the back of my mind I really felt that the 58L head would probably have larger valves/porting and although I have not physically had the opportunity to compare the 58L head valves and cams I suspect that this is the case because although I can get the 36mm carbs to sync up and come to a lovely blue on the colourtune at idle, it just kills the engine with a bit of a blap on the throttle.
    So...
    I remembered a ways back when I started with the conversion from the 37h to the 31a motor I had attempted to use a set of 36mm mikunis that I had swapped all the jets out of the 35mm mikunis into and ended up with some serious flooding issues at freeway speeds.

    I was hoping that I had solved that with the 58L piston upgrade but... alas!

    popped the 35mm mikunis back in and the motor is running a charm.

    Doing a few modifications, new LED indicators and warm white LED globes in dash and HUD display implementation before I actually take it for a spin.
     
    chacal likes this.
  3. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    First real test today.
    Ran like a champ, was way too tempted to twist on but held back.
    From the sitting on top perspective and the new home made 4 into 1 system with the Kwaka titanium muffler it seems to sound a bit like a damn subaru at slow acceleration... I'm not sure what thats about but I only did 40Kms in the city today with a short 100km/h stint on the freeway.
    Bit of vibration and a bit of idle hang but nothing that is dissuading.
    Will be testing the main jets and resyncing/colourtuning at the 500km point after some new oil and when I can twist on.
    Happy chappy :)
     
  4. MattiThundrrr

    MattiThundrrr Not a guru

    Messages:
    3,690
    Likes Received:
    1,665
    Trophy Points:
    113
    Location:
    America's friendly hat
    That could be a problem. Subarus have a boxer engine, which explains their lumpy sound. If an inline four is doing it, it could be misfiring. Should sound smooth and even.
     
    Chitwood likes this.
  5. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Haha yes it would be a problem.
    Sorry I just mean't it sounds weird... and I dislike subarus... because some wanker drives one down my street every day and makes my dogs bark like lunatics.
    The 4 into 1 I built is nice and simple with simple baffles and I am paying attention to all the noise, albeit mild in comparison. (to that damn subaru)
     
  6. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
  7. MattiThundrrr

    MattiThundrrr Not a guru

    Messages:
    3,690
    Likes Received:
    1,665
    Trophy Points:
    113
    Location:
    America's friendly hat
    I drive a Subaru, which I love. Affordable all wheel drive wagon, seat and WIPER heaters! Great for Canadian winters. Except for the damned oil leak which drips on the exhaust and stinks up the cabin. Another effect of the boxer engine design- oil sits on the seals all the time and eventually leaks through. Happened to my last subie as well.:confused:
     
  8. joe elliff

    joe elliff Active Member

    Messages:
    666
    Likes Received:
    241
    Trophy Points:
    43
    Location:
    illinois
    Yes. That may be true matti but about 2 hours of labor and you can have that motor out and freshened up with new seals and back in. I did it many times with my 1.8 and once with the 2.5. Easy peasy. I don’t currently have any subies in my garage :(. I absolutely love them tho myself. With a normal exhaust system tho. Haha

    Now I’m off to see the aforementioned link for the 4-1
     
  9. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    I have become enamoured with the sound of exhaust system now, probably because the bike is a monster now with the fresh boring.
    Bike is going a charm. Nearly time for the first oil change and tune up.
     
  10. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods
    I have seen people bring their bikes into the house but never their automobile;)
     
  11. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Final.
    Just did the post-run-in tuneup.
    2 shims needed to be changed, 3 carbs needed the air-mix altered, the rack needed minor syncing.
    Plugs were brown... sweet! I won't be doing any re-jetting by the looks.
    All worked out well.
     
    chacal likes this.
  12. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Final.. Final... :(
    Sad news!
    I have decided to take a step back and re-instate the 33F bores/pistons to this engine... sounds extreme but the reality is I have not been able to get around a simple fact and that fact is heat.

    The bike rides like a dream as long as the external temperature is sub 18 degrees C which in perth is only at night or the middle of winter and the rest of the time the bike will overheat so badly that sitting at a set of lights on a 24 degree C day is burning my legs...

    At any rate the actual steps I've taken to try and remedy the issue are quite extensive and mainly based on fuel mix/level and the plain riding outcome is that once the bike is too hot there is no slide lift between idle and 3000 RPM.
    I've gone to extremes in all directions
    - replaced carb intake manifolds (no difference)
    - replaced vacuum caps and hose with silicon (no difference)
    - drilling slide holes (more responsive)
    - adding slide holes (more responsive)
    - clipping springs (more responsive - flutters)
    - reducing main jet size by 10 (more responsive - midrange lost)
    - reducing air flow (fouling)
    - increasing air flow (no difference)
    - adding heat sinks to headers (longer till overheat)
    - running super lean idle mix (popping - no difference)
    - running super rich idle mix (fouling - no difference)
    - replacing TCI (no difference)
    - replacing the pickups and rewiring the harness back to the TCI (no difference)
    - altering the timing as much as possible each way with a timing light (crisper)

    I suspect the 33F head is where the issue lies due to the smaller valve sizes plus the fact that the 58L specifications show it has a lower vacuum than the 33F, if I end up finding a 58L head and cams I will probably revisit this for the cost of a head gasket... or not!

    A great learning curve as I can now see and feel what each of these extremes do but... as soon as this beast gets hot... back to being a bicycle when trying to take off or accelerate from within the idle circuit range.

    So I guess... a cool climate modification only. Then again I wouldn't take that statement as a given.

    Oh well.
     
  13. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    Haha...
    Feel like the 'the monster at the end of the book' now.

    Shame on me.
    TCI was faulty, who'd of thought.
    Changed from an obviously faulty TCI to a faulty 2nd hand Hyperpak, from ebay, TCI.
    What are the odds?
    At any rate this means that all my EXTREME efforts to sort this out were electrical and after reverting to the 33F pistons and cylinders and still having the same issue I pulled the original standard TCI apart, replaced the capacitors, resoldered everything else and the issue was gone.
    Sucks... but I'm holding onto the 58L Pistons and bored barrels for the next iteration of insanity I persue.
    Grrr... but... the bike runs pretty good so there is that.
     
    Simmy likes this.
  14. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,854
    Trophy Points:
    113
    Location:
    Great North Woods


    TALKIN' TECH: Various thoughts on various issues

    " The pilot fuel circuit is active from idle up to about 2500-3500 rpms, and at about 3000 rpms the main fuel circuit starts becoming involved, and by 4000+ rpms the main fuel circuit is responsible for about 80%+ of the engine's fuel supply conditions"

    if I am understanding the above statement . I do not think the slide lifts before 3000 rpm. if they do lift the mains are kicking in.
     
  15. cds1984

    cds1984 Active Member

    Messages:
    902
    Likes Received:
    195
    Trophy Points:
    43
    Location:
    Perth, Western Australia
    That made perfect sense and is also the reason why I entertained the insanity approach trying to nail it down.
    The question I should have asked myself is why did I get an ERD hyperpak to suit the XJ900 motor so cheap on ebay.
    But I should have asked the question before I purchased it... obviously.

    A hard lesson in not trusting 2nd hand parts.

    On the plus side, a HUGE sense of satisfaction making the original faulty TCI do the job.
    *sigh*
     

Share This Page