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Jeff Shackell
United Kingdom
42 Posts |
 Posted - 29/01/2012 : 09:43:51
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Good morning all
Can anyone tell me what size and type of S U Carburetter is fitted as standard to the J2. Our attention with my car here is now focusing on possible problems with the carburetters and the totally frustrating misfiring problems. Regular posters here have helped and commented before on my J2 misfire. With the engine now running very well and this weeks activities looking at the brakes to make it stop, the misfire is incredibly still with me.
New plugs, changed plugs, cleaned plugs, new coil, new condenser, completely checked over distributor, the fuel pump looks new or certainly very recent, fresh fuel but still at will and without notice it will decide to misfire. It can be fine one hour and not the next.
The rear plugs seemed to be more black than the front two, could it be something to do with the carburetter flooding and causing problems. In trying to locate which cylinder or cylinders are playing up, it can change its mind over misfiring within the time one begins to think about it.
As a reminder, not being very knowledgeable I'm only poking about in the dark in these matters.
Thanks again for help and suggestions in the past.
Jeff |
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Richard Hardy
United Kingdom
2159 Posts |
Posted - 29/01/2012 : 10:29:32
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Jeff
The original size is 1 inch dia (from the manifold side), 7/8th from the intake side.
I assume you have checked the the ignition timing. Do you have the valve timing correct also? The lobes on the cam for no.1 cylinder should be at 11 and 1 o'clock positions (equally) when at TDC.
Also, have you checked the condenser. The obvious sign of fault here is that the car will run perfectly up until a certain temperature and once there, misfire, or complete failure can occur
I assume you have set your forks correctly in the float chambers to avoid flooding or starvation into the carb?
Lastly, check the fuel pump. Again, these can create a misfire when reaching a certain temperature. I once rebuilt my mag only to then find it was the pump!
Hope this helps
Rich
Vintage MG Parts |
Edited by - Richard Hardy on 29/01/2012 10:31:44 |
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Bill Abbott
United Kingdom
61 Posts |
Posted - 29/01/2012 : 10:53:16
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Jeff I would try and borrow a distro cap and rotor arm that you know to be ok. My T type had an inconsistent misfire that was down to a poorly made rotor arm. Once changed for a decent one the troubles went with it.You look at the rotor arm and think what could possibly go wrong with it, but they can and do track down to earth.
Good luck Bill |
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george
United Kingdom
862 Posts |
Posted - 29/01/2012 : 11:29:46
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| I agree with Bill over the years I have had more bother with rotor arms than any other single component .I think a lot of very poor quality lookalikes are on the market Geoff |
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spitfire
United Kingdom
371 Posts |
Posted - 29/01/2012 : 11:54:35
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Can you get one of the new Red rotor arms (that are designed with compounds that stop the shorting) for this?
Having a Spitfire engine in mine leaves me none the wiser on J2 powerplants.
It's a suggestion to put to those in the know. Dead cheap way to banish a sod of a problem. |
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Jeff Shackell
United Kingdom
42 Posts |
Posted - 29/01/2012 : 13:00:01
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Thank you for your replies. I have been out in the J2 this morning and it did not miss a beat! The engine has been very well timed from the ignition point of view, we have not quite got to the valve timing matter but when it is running it goes very well and I think would keep up with my PB. I could have said all this last week though and yet by midweek it was misfiring shocking. It all remains a mystery but interesting all the same!
Thanks again.
Jeff |
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Peter Green
United Kingdom
1682 Posts |
Posted - 29/01/2012 : 14:15:21
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Jeff,
Do you have any misfiring problems on the PB? If not fit the distributor from the PB onto the J2 and see if it still misfires, if it does you know it is nothing to do with the distributor.
Peter. |
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