Series MM highlight carb problems?

for those with Series MM sidevalve cars produced between September 1948 and February 1953

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gtt1951
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Series MM highlight carb problems?

Postby gtt1951 » Tue Mar 13, 2018 5:06 pm

Hello folks, I've been trying to get my Series MM fired up to drive it out of it's PolyTunnel, for birthday photos tomorrow - both of us entered the world on the same date.
It has a H1 carb, , that I had "refurbished" soon after buying he car, a few years ago, as it was leaking (using an SU kit bought from Burlen Ltd).
It seems to have a small leak from the needle adjusting screw again, whilst attempting to get it going.

Symptoms - 918 sidevalve engine, Fuel in tank (1/2 gal of fresh added), fuel pump pumps, float chamber full of fuel, spark on all 4 plugs, although yellow, dizzy has a +ve earth electronic conversion inside, plugs don't smell of petrol and the pump doesn't "tick" that much when I'm turning the engine over.
Took air silencer off, lifting piston with finger is very stiff, very easy if dash-pot damper removed.
Engine last fired up a few months ago - I know, should do it more often, but hadn't been well.

A few hours work, over 2 days, has just made my back worse, so have given up trying things out and am asking here for some advice.

Could it be anything to do with the needle or its seat? Any help gratefully received.

George.
Last edited by gtt1951 on Tue Mar 13, 2018 6:39 pm, edited 1 time in total.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

RobThomas
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Re: Seriess MM highlight carb problems?

Postby RobThomas » Tue Mar 13, 2018 5:54 pm

Slacken the 2 dashpot screws a little and lift the piston. Tighten a touch and see if the piston had been pinched.
Hopefully it can be lifted and then drops down to the bottom cleanly with the damper rod out. If so, put a teaspoon of new petrol down the carb intake and fire it up with the choke off. It will go rich-> lean so you'll know if it is fuel related. If it won't fire it should be a sparky problem.
Cardiff, UK

gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Tue Mar 13, 2018 6:35 pm

Rob, thanks, I'll have to try that in daylight tomorrow morning.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

philthehill
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Re: Series MM highlight carb problems?

Postby philthehill » Tue Mar 13, 2018 7:32 pm

The needle fitted and secured in the damper does not have a seat and does not seat on the jet.
If you have a leak it will not be from the needle or its seat but the from the jet seals.
The seals are cork and will dry out if not used. A common occurrence.
The float chamber does have a needle and needle seat which is prone to leakage and shows itself by flooding the carb or overflowing float chamber.
If you have fuel, the pump is working and the fuel is not stale the problem will be with the ignition.


gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Tue Mar 13, 2018 7:42 pm

Phil, the spark does look a bit weak. Whilst not being used what could be the cause of the deterioration?
Could it be the coil output? [shudder to think if Roy were to see this from the other side].
As far as I am aware, it is the original coil fitted in 1951.
I can always revert back to the original dizzy set-up and will just have to change the timing about about 8 deg.

Anyway, this will have to be for day-time work and I'm doing a trip to Brighton for my birthday, tomorrow, so no pics on the road, of both me and the black saloon (short-bonnet), known as MM Sweetie.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

philthehill
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Re: Series MM highlight carb problems?

Postby philthehill » Tue Mar 13, 2018 8:05 pm

Personally I would revert back to the original specification ignition /dizzy system as that appears to be a known quantity and go from there.
Have a nice birthday tomorrow. Brighton is very nice.
Last time I was there I was competing in the Brighton Speed Trials. Below approaching the start line.
Have a nice day even if you are not driving Sweetie. There will always be another birthday for you both.
Phil
Attachments
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gtt1951
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Re: Seriess MM highlight carb problems?

Postby gtt1951 » Thu Mar 15, 2018 12:25 pm

RobThomas wrote:... If so, put a teaspoon of new petrol down the carb intake and fire it up with the choke off. It will go rich-> lean so you'll know if it is fuel related. If it won't fire it should be a sparky problem.
Thanks Rob and Phil for the replies so far -
"a spoonful of petrol helps the engine start up..."

I didn't get to try anything on my Birthday as was out for the day. Had a go this morning - looks like I'll be taking the carb off and fiddling "on the bench". Ignition is OK.

Updates later.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Thu Mar 15, 2018 2:03 pm

Carb is off the manifold and will be stripped down. There is one strange thing - there is no internal damper spring!
I've looked at my old pictures where I did the original refurb and can't see a spring in those pictures eirther!
Should the H1 carb have a spring - Burlen show a spring in the parts blow-up diagram (part No. 2) but don't list it in the list of available parts.
Also, is the special manifold gasket - see pic - are replacements available?
Attachments
manifold gasket-resized.jpg
manifold gasket-resized.jpg (51.18 KiB) Viewed 1024 times

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

philthehill
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Re: Series MM highlight carb problems?

Postby philthehill » Thu Mar 15, 2018 4:02 pm

I am glad that you enjoyed your birthday. :D

The special gasket is a fuel diffuser. It was a popular item way back in the 1940s & 1950s in an attempt to get better combustion and more miles per gallon.

As regards the spring - not all HI carbs had the spring, some had a weighted damper piston.

Could you please post a picture of the carb damper piston.

Phil


gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Thu Mar 15, 2018 5:04 pm

Phil, here is a picture of the damper piston.
Damper piston-resized.jpg
Damper piston-resized.jpg (113.1 KiB) Viewed 1012 times
So what is that you see in the background to the damper shot?
spare engine-resized.jpg
spare engine-resized.jpg (236.21 KiB) Viewed 1012 times
It is a spare H1 carb!
Found it on the spare 918 engine I bought a couple of years ago.
The spare engine has different carb mounts - 2 x thick gasket.
spare engine carb mounts.jpg
spare engine carb mounts.jpg (246.01 KiB) Viewed 1012 times
The spare damper is below
spare-piston-resized.jpg
spare-piston-resized.jpg (83.72 KiB) Viewed 1012 times
The "spare" carb is currently soaking in some PlusGas as the piston is surface corroded and I can't separate the cover from the carb body at the moment, so can't see if that has a spring.
Attachments
spare carb-resized.jpg
spare carb-resized.jpg (183.35 KiB) Viewed 1012 times

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

philthehill
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Re: Series MM highlight carb problems?

Postby philthehill » Thu Mar 15, 2018 5:43 pm

Thank you for the pictures.
What I was really meant when I said damper piston was the main carb piston that the needle is attached too.
If you could post a picture of the main piston (especially the top of the piston) that would be great and I will be able to determine if the piston is weighted or not.
Phil


gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Sat Mar 17, 2018 11:54 am

Phil, very sorry, I misunderstood. I think that you are correct and the pistons are weighted - they certainly feel heavier than the other models.
piston-1-resized.jpg
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Piston-2-resized.jpg
Piston-2-resized.jpg (92.14 KiB) Viewed 960 times
Piston-3-resized.jpg
Piston-3-resized.jpg (101.57 KiB) Viewed 960 times
The above are images of the piston from the carb that was fitted. Below is an image of the "spare" which also doesn't have a spring.
Piston-spare-resized.jpg
Piston-spare-resized.jpg (139.97 KiB) Viewed 960 times
Overnight I had a thought - that the carb problem may be due to a blockage, so I have just used a computer cleaning air can to blow through the bottom of the float chamber - don't want to dismantle too much, at this stage, until I get spare bits from Burlen - just missed 2 sets of washers and gaskets on eBay (yesterday).

It is snowing and the temperature has dropped, so not likely to want to go out to the polytunnel and under a bonnet just now.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

philthehill
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Re: Series MM highlight carb problems?

Postby philthehill » Sat Mar 17, 2018 3:35 pm

Thanks for the pictures of the main carb piston.

The main carb piston is weighted so there is no need for the spring.

The H1 SU carb is different to the HS2 SU carb in that the jet is fed through the float chamber to carb main body lug and not through a external pipe as per the HS2.
Whilst there is a filter in the SU fuel pump fine sediment still gets through and solidifies in the bottom of the float chamber and float chamber lug.
One way of clearing the blockage is to rev the engine and then put your palm over the carb mouth and let the manifold vacuum pull the sediment through.
It may take a couple of goes but it usually works well.
Phil


sparesman
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Re: Series MM highlight carb problems?

Postby sparesman » Mon Mar 19, 2018 11:01 pm

I have rebuilt the H1 carb several times over the years for the various MMs I have owned since early 80s and none originally had a spring in them, although occasionally I have retro fitted a spring to help the piston close down better. Often it is a matter of loosening the two dashpot screws slightly then the piston will move up and down easier, then retighten.
Incidentally we have a good supply of H1 seal and gasket kits in the club stocks cheaper than Burlen and are genuine SU parts. When installing you should soak the cork filter in oil for a day to make it more flexible when fitting.
Bryan Gostling
1952 MM 2dr saloon in Thames Blue UNO212
1953 S11 Traveller in Birch Grey - oldest survivor ? Export model now reg PPO924
1953 S11 Traveller in Black - 3rd oldest PPX344

gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Fri Mar 30, 2018 2:50 pm

Thanks everyone for all the information and suggestions
Both H1 carbs are now in pieces. I thought that I had already worked on the fitted one I was having problems with but, it is obvious from the pieces, that I couldn't have done much work on it at all (apart from stopping the original leak when I bought the car).
OK, so I now have one Burlen SU Gasket Pack (AUE 900) but, as the "spare" carb didn't even have some of the brass (and cork) washers that go either side of the spring on the needle guide, I will need another gasket pack from Bryan.

By the way, I think I've twigged what the problem was, having got my Nitrile gloves covered in "fuel" when doing Phils' trick of clearing sediment, the gloved hand did NOT smell of petrol, but more like emulsion paint! All I managed to do, during my tests, was to put some good petrol in on top of the bad stuff in the tank.
The teaspoon (or couple) of fresh fuel, in the earlier suggested tests, fired the engine up, of course. But when I tried this again, with the carb refitted, it didn't work as I was using fuel that had been pumped up from the tank.
I have pumped all this out now and will put in more than just 5 litres, when the carbs are ready to test, just to make sure that any duff fuel left in the tank gets thinned out.

Bryan, how much for a gasket pack from Club Spares?

George.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Wed Apr 25, 2018 6:09 pm

All done and its Alive!
Carb has been refurbished and fitted yesterday. Fresh fuel in the tank (about 8 litres). Tried starting, but I had run down the battery with the original attempts :( and the Solar Trickle charger hadn't refreshed it :oops:
Put battery on charge (boost for the afternoon and then trickle overnight) and finished job today. Lovely - its nice to hear it running again - will need a "round the block" trip on a dry day to clear the cobwebs.
Now just need to do the same to the H1 carb that came with the s/h "spare" engine - jet head lever assembly (and choke connecting arm) looks quite different on this one - a different angle.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.

sparesman
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Re: Series MM highlight carb problems?

Postby sparesman » Sun Apr 29, 2018 8:33 pm

Your spare carb looks as if it has the bracket and brass lever as used on the Series 2 version of the H1 carb.
Bryan
1952 MM 2dr saloon in Thames Blue UNO212
1953 S11 Traveller in Birch Grey - oldest survivor ? Export model now reg PPO924
1953 S11 Traveller in Black - 3rd oldest PPX344

sparesman
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Re: Series MM highlight carb problems?

Postby sparesman » Sun Apr 29, 2018 8:33 pm

Your spare carb looks as if it has the bracket and brass lever as used on the Series 2 version of the H1 carb.
Bryan
1952 MM 2dr saloon in Thames Blue UNO212
1953 S11 Traveller in Birch Grey - oldest survivor ? Export model now reg PPO924
1953 S11 Traveller in Black - 3rd oldest PPX344

sparesman
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Posts: 302
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Re: Series MM highlight carb problems?

Postby sparesman » Sun Apr 29, 2018 8:33 pm

Your spare carb looks as if it has the bracket and brass lever as used on the Series 2 version of the H1 carb.
Bryan
1952 MM 2dr saloon in Thames Blue UNO212
1953 S11 Traveller in Birch Grey - oldest survivor ? Export model now reg PPO924
1953 S11 Traveller in Black - 3rd oldest PPX344

gtt1951
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Re: Series MM highlight carb problems?

Postby gtt1951 » Mon Apr 30, 2018 11:14 am

Bryan, it was definitely mounted on a 918 side-valve engine - maybe a previous owner had used a "newer" carb.
I'll check to see what I have on the 803cc engines (one fitted in my Grey 4-door, the other is a "spare" engine).
George.

'51 Hi-light with Sidevalve 918 engine,
'55 4-dr with 803 engine,
'56 Traveller with 1098 engine.


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