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Old 4 Weeks Ago   #1
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126 650cc engine transplant..

Morning All


Done a quick search and seem to have a few conflicting responses so bear with me when I ask the following...


1, If I got a 126 650cc complete engine box and drive shafts what would it entail to swap it with the standard 495cc lump?


2, Everything is standard at the moment on both the 495 and 650 lumps, other than the synchro box benefit is it worth doing for the extra horses gained?


TIA


Rob
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Old 4 Weeks Ago   #2
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Re: 126 650cc engine transplant..

The simple answer is:---yes, it is worth the swap. The extra power will make driving in modern traffic less stressful as you will be able to keep up with the flow of traffic much more easily.
Whilst it not a difficult swap it is not 'one out--one in', there are differences that have to be addressed. The main one is the drive-shafts--the 126 shafts are too long and will have to be exchanged for 500 shafts (24/25mm). The 650 '126' engine has an alternator (500, a dynamo) so there is a small change to the electrics required. If the 650 engine has a 'cable' starter, you can retain the 500s activation lever---but you must use a 650 starter.
There is a good chance that the 650 engine has a 28IMB Weber carb which has a 'fuel return' outlet at the top of the carb---I would suggest that you utilise this and put a simple return into the fuel system (round the back of the trunking and down to a METAL 'T' piece fitted just before the fuel pump). By having the fuel constantly moving, it keeps a bit cooler, which helps with 'hot' starting.
I am sure that other Forum members will come with other little 'swap glitches' but these ones are the main ones.
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Old 4 Weeks Ago   #3
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Re: 126 650cc engine transplant..

Definitely following this post as I just today bought a 126A1 engine to build up and swap.
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Old 3 Weeks Ago   #4
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Re: 126 650cc engine transplant..

Quote Originally Posted by the hobbler View Post
The simple answer is:---yes, it is worth the swap. The extra power will make driving in modern traffic less stressful as you will be able to keep up with the flow of traffic much more easily.
Whilst it not a difficult swap it is not 'one out--one in', there are differences that have to be addressed. The main one is the drive-shafts--the 126 shafts are too long and will have to be exchanged for 500 shafts (24/25mm). The 650 '126' engine has an alternator (500, a dynamo) so there is a small change to the electrics required. If the 650 engine has a 'cable' starter, you can retain the 500s activation lever---but you must use a 650 starter.
There is a good chance that the 650 engine has a 28IMB Weber carb which has a 'fuel return' outlet at the top of the carb---I would suggest that you utilise this and put a simple return into the fuel system (round the back of the trunking and down to a METAL 'T' piece fitted just before the fuel pump). By having the fuel constantly moving, it keeps a bit cooler, which helps with 'hot' starting.
I am sure that other Forum members will come with other little 'swap glitches' but these ones are the main ones.

If Carlsberg did forum responses...


That's exactly what I was looking for, thank you....


Looks like a road trip on Saturday then....


The wife is going to kill me as we are moving soon and I currently am doing an engine swap in my VW beetle


I'll look at taking pic's and doing a bit of a build study on it. Will have to understand how to post pics too... (answers on a post card)


Thanks again Mr Hobbler....
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Old 3 Weeks Ago   #5
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Re: 126 650cc engine transplant..

Ooh yes Id love to see the transplant thread. Have the swap on my one day list
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Old 3 Weeks Ago   #6
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Re: 126 650cc engine transplant..

Picking the engine/box up on Saturday morning so it would be only right to start with a pic of it before I pull it apart to rebuild it all.....


Just to advise it will be a long drawn out thread so don't get too giddy


Rob
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Old 3 Weeks Ago   #7
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Re: 126 650cc engine transplant..

All the best with the engine transplant. To make it easier to work on, may I suggest that you get a cheap engine rottiserie---(a) the engine will be at an 'easy to work on' height and, (b) you will be able to spin the engine over as required.
I have put together, from my experience of building my own tuned engine and my time at Radbourne Racing, my thoughts on how to tune the '126' engine. As well as how to tune the engine, it includes some sensible 'enhancements' on even a standard engine. If you would like a copy of these thoughts (sounds almost Maoist), contact me directly and I will put them through to you---- tommontagu@yahoo.co.uk
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Old 3 Weeks Ago   #8
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Re: 126 650cc engine transplant..

Quote Originally Posted by the hobbler View Post
All the best with the engine transplant. To make it easier to work on, may I suggest that you get a cheap engine rottiserie---(a) the engine will be at an 'easy to work on' height and, (b) you will be able to spin the engine over as required.
I have put together, from my experience of building my own tuned engine and my time at Radbourne Racing, my thoughts on how to tune the '126' engine. As well as how to tune the engine, it includes some sensible 'enhancements' on even a standard engine. If you would like a copy of these thoughts (sounds almost Maoist), contact me directly and I will put them through to you---- tommontagu@yahoo.co.uk




Morning, I have emailed you regarding.....
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Old 3 Weeks Ago   #9
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Re: 126 650cc engine transplant..

The hardest part about the swap for me was getting the hot air duct to miss the starter. P.S. don't forget to swap the driveshafts.
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Old 3 Weeks Ago   #10
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Re: 126 650cc engine transplant..

I did this a few years ago - well worth it. I live in a very hilly area and the conversion makes the car much more usable.


Prior to fitting, I rebuilt the 652cc engine as a 695cc.


Chris
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Old 3 Weeks Ago   #11
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Re: 126 650cc engine transplant..

Ok so its in the garage, major strip down starts tomorrow as I have to sort it in two weeks as we want to drag the 500 to Cornwall behind the motor home when we go away.....
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Old 3 Weeks Ago   #12
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Re: 126 650cc engine transplant..

Just a quick one, its been mentioned that the 650 lump runs an alternator not a dynamo and mods to the wiring is required, cant the dynamo just be reused?
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Old 3 Weeks Ago   #13
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Re: 126 650cc engine transplant..

Simple answer---no! The alternator and the dynamo have different mounting methods to the crankcase and the aperture in the fan housing is of a slightly different shape. It HAS been done, but the person who did it said, and I quote, "never again".
I am not an electrician, but I have been told that it is not a difficult mod. !st of all though, which type alternator is on your 'new' engine---the early 650s had a completely remote regulator, the later ones had an integral regulator. On some, the regulator is a small unit bolted to the casting (part of the alternator) that bolts to the crankcase. If you can let the Forum know which one you have, I am sure that the 'electrical brains' can let you know how to re-wire the system.
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Old 3 Weeks Ago   #14
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Re: 126 650cc engine transplant..

Quote Originally Posted by The Whitakers View Post
Just a quick one, its been mentioned that the 650 lump runs an alternator not a dynamo and mods to the wiring is required, cant the dynamo just be reused?
Definitely simpler and quicker to keep the alternator and would usually be argued that this is an improvement too.

I have done this in reverse and fitted an alternator to a 499cc engine by transferring the cowlings from the 652cc engine. So you could achieve your requirement by putting those from the 499 on the 652.

The alternator has an integral mounting plinth and fixes to the crankcase using setscrews. The dynamo has a separate mounting-cradle which is secured using nuts on studs into the crankcase. But all alignments and geometry were the same in my experience; the job was no more mind-boggling than anything else I've encountered on a 500; the alternator fits over the studs so the dynamo-cradle should fit using the setscrews.

I found it simpler in the end, regardless of which permutation of cowlings is used, to fit the heater-duct designed for the 500R/126 in place of the original; this avoids undesirable contact with the starter-terminal. You also need to fit a 126 starter-pull-cable and obtain a small, nylon cable-stop which fits underneath the heater-duct. Ideally you can also replace the heat-shield above the exhaust with the one off the 500R. There was some disagreement with me but I prefer the 499 rocker-cover on the 652 engine when fitted in a standard 500 because the HT-lead mounting bracket makes the leads abrade on the engine-lid. You also need the longer studs into the timing-covet for the engine-mounting.

I discovered most of the above by trial and error but I benefitted from a lot of guidance from some very helpful contributors here.

I would be very cautious about trusting an unknown engine, on an important journey, to give you reliability after the various modifications that will be needed. Ideally you would need quite a few miles of shakedown to get everything running just right.
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Last edited by fiat500; 3 Weeks Ago at 23:32.
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Old 3 Weeks Ago   #15
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Re: 126 650cc engine transplant..

Quote Originally Posted by fiat500 View Post
Definitely simpler and quicker to keep the alternator and would usually be argued that this is an improvement too.

I have done this in reverse and fitted an alternator to a 499cc engine by transferring the cowlings from the 652cc engine. So you could achieve your requirement by putting those from the 499 on the 652.

The alternator has an integral mounting plinth and fixes to the crankcase using setscrews. The dynamo has a separate mounting-cradle which is secured using nuts on studs into the crankcase. But all alignments and geometry were the same in my experience; the job was no more mind-boggling than anything else I've encountered on a 500; the alternator fits over the studs so the dynamo-cradle should fit using the setscrews.

I found it simpler in the end, regardless of which permutation of cowlings is used, to fit the heater-duct designed for the 500R/126 in place of the original; this avoids undesirable contact with the starter-terminal. You also need to fit a 126 starter-pull-cable and obtain a small, nylon cable-stop which fits underneath the heater-duct. Ideally you can also replace the heat-shield above the exhaust with the one off the 500R. There was some disagreement with me but I prefer the 499 rocker-cover on the 652 engine when fitted in a standard 500 because the HT-lead mounting bracket makes the leads abrade on the engine-lid. You also need the longer studs into the timing-covet for the engine-mounting.

I discovered most of the above by trial and error but I benefitted from a lot of guidance from some very helpful contributors here.

I would be very cautious about trusting an unknown engine, on an important journey, to give you reliability after the various modifications that will be needed. Ideally you would need quite a few miles of shakedown to get everything running just right.

Thanks for the info, I have not even looked at the wiring as yet with a consideration of what to do if I kept the alternator, ill look to see if there is a thread relating to the exchange. Rebuilding the 650 lump wont be an issue for me but like you say it's the integration of it into the 500 and ensuring everything works works ok will be the issue. Another major concern is that I am quite unfamiliar with the whole 500 workings too....


Not sure why I have these crazy ideas and set these stupid time scales.....


Rob
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