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Fulmar trouble - fuelling?

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Fulmar trouble - fuelling?

Post  fulmar88 on Sun Jul 24, 2016 11:49 am

Hi all,  20 miles from home yesterday out of the blue my Fulmar suddenly lost power. For some reason I went immediately to the choke and closed it slightly. Fairly normal running resumed and as soon as I removed the choke it started struggling again. After a couple of miles I stopped in order to turn back towards home. The bike stalled. I struggled for 10 minutes to get it going which included changing the plug. I didn't touch the tickler as normally it starts hot ok. When it did start it was spitting and banging and wouldn't run clean without choke. At various points on the way home I had to play with the choke to keep it running. Occasionally it really slowed and backfired etc. When I got home fuel was dripping from the carb. When it stalled and I changed the plug fuel was not dripping. It seemed that I was getting insufficient fuel at times and then too much at others. I stripped the carb and found that the float had moved sideways along its pivot shaft and allowed the needle to fall adjacent to the plate it should sit on. This explained the flooding. My only thought about the initial problem of a weak mixture is that as the float moved sideways it was preventing the needle freely falling initially. I'm not convinced the offending bush that keeps the float in place isn't a homemade one. I've throughly cleaned the carb and didn't find any reason for fuel starvation but before I reassemble is there any other explanation for the symptoms I experienced? The carb is a 375 Amal monobloc for those not familiar with the Fulmar.

Steve
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carb woes

Post  piston 197 on Sun Jul 24, 2016 4:11 pm

Steve, exactly the symptoms you will get if the pilot jet blocks up, remove the jet clean and with a bit of thin wire ( braid from a cable will suffice) make sure the pilot hole into the body is clear ? ( small hole that exits in line with the jet into the body of the carb about 1/2" from edge of flange
JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Sun Jul 24, 2016 5:15 pm

Thanks John. I'd already removed the jets and checked / cleaned. The pilot jet was partially blocked but I dismissed this as the cause of my troubles as it seemed so insignificant and I didn't realise it could have such a dramatic effect. I'll order a new gasket set later and see how it goes. There was a fair bit of brown silt in the main jet cover so plenty is getting past the filters (2) although it is very fine. I've just checked the hole in the body and it is clear.
Steve.
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Mon Jul 25, 2016 6:46 pm

Whilst cleaning my carb I noticed that it is a 375/49 (stamped on the flange). According to the book the Fulmar should have a 375/37. In the Amal site searching for Fulmar sure enough brings up a 375/37 as it does for a Plover 86 and 95.  But, if you search for FB 15T 2 stroke it lists both. The 375/37 from '58-'61 and the 375/49 from '62 on. As far as I can see none of the FB specific models list the 375/49 only the FB 15T 2 stroke. The spec appears to be identical. Could the FB instruction book be wrong and is just listing the spec for a Plover 86 (the preceding 15T model date wise). What have other Fulmar owners got in their bikes? My bike is very original and has never been restored so I'm curious to understand if the carb has been replaced and what the differences are between the 2 types.

Steve.
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carb differences

Post  piston 197 on Mon Jul 25, 2016 7:12 pm

Now here is where I get a bit "anoraky"
the plover 86 up 1962 used the 375/49 carb and the Plover 95 and Fulmar 88,90 used the 375/37
all parts, jets diameters etc are the same except the Banjo part No , the 375/49 uses banjo part No 376/127, and the 375/37 uses the Banjo part No 376/138
Special details for the 375/49 says "Less air tube, rod controlled air valve"
special details for the 375/37 says "spray tube376/136, Rod controlled air valve"

So reading between the lines it looks as if there is Bu**er all difference as regards running is concerned, presumably with the Plover 95 and the Fulmars a different angle of fuel banjo was used as the extra tin probably meant the standard 90deg. one was obstructed by tinware ??

The James SC Scooter also used the 375/37 and that engine was laid down horizontally
JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Mon Jul 25, 2016 8:02 pm

Thanks John. Ironically the original banjos are not available for either and a new 375/37 or 375/49 get supplied with the same alternative. It seems strange that the Fulmar had a rod controlled air valve version as it would be very difficult to find it on the move up inside the panelling. The rod is not available either so to all intents both versions new are now identical with a cable operated choke. What it does mean is my carb has been changed and that the Amal site is somewhat incorrect in what it says is specified for what.
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Amal site

Post  piston 197 on Mon Jul 25, 2016 8:24 pm

I did not refer to the AMAL site I used the old fashioned AMAL dealer specification sheets issue by Amal, one dealing with 1955 to 1961 bikes and one 1962 to 65, so presumably AMAL on line just repeats this info, so if it is wrong it must have always been wrong back in the day ?

JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Mon Jul 25, 2016 8:34 pm

John I was saying that the Amal site is different to what your sheets say and therefore it was wrong. Possibly because the carbs are now essentially the same they list the 375/37 for both Plovers and the Fulmar. They only list the 375/49 as suitable for a 1962 15T. I would still like to know what everyone else has on their Fulmars and the type of choke fitted though.
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Tue Jul 26, 2016 5:22 am

John, I've remembered that my choke cable still has the original Romac label on it which may help decide what my carb was fitted to originally. The number is T378. Do you have a list of fitments?

Steve.
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air cable

Post  piston 197 on Tue Jul 26, 2016 5:51 am

Steve I would be surprised if FB would send out cables on new bikes with Romac labels as they sold their own cables as spares ( probably made by Romac anyway), but to further muddy the water
T378 is an Air cable for a BSA A7 1948/59 and a BSA A10 1949/57.
The Romac catalogue only specifies air ( choke ) cables for the Cruiser 80 and 84 which is TG542, which in itself is odd as the Falcon 81 and the Falcon 87 also used a choke cable on some years ?

Cables listed for the Fulmar 88 in the Romac catalogue are
F/Brake T911
Clutch T910
Throttle T912

as each new design took the next available No 900 series Nos. were from about 1961 0nwards and T378 would have a date of approx. 1947

JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Tue Jul 26, 2016 6:09 am

Ah well that explains why it meanders somewhat before it gets to the carb. I guess it's a little longer than necessary.

Steve.
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More confusion

Post  fulmar88 on Thu Aug 04, 2016 12:41 pm

Regarding the comments above about the Fulmar having a rod operated choke, and no cable being specified in the spec sheets, I have noticed that the manual choke lever on my bike sits in a cut-out in the handlebar cover. I have found half a dozen fulmar pics online with the same cut-out and the choke sitting in it (example below). I wonder if this was either introduced soon after launch as the rod choke would be impossible to use unless you are off the bike, or the spec sheets are wrong in listing a rod operated choke. The absence of a choke cable in the listings further confuses things if this was indeed there from launch. Furthermore I have found a few examples online of the banjo inlet coming from underneath as it does on my bike, but two examples for sale on ebay of 375/37 carbs (the Fulmar spec) have it coming in from above.




Steve.
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curiouser and curiouser

Post  piston 197 on Thu Aug 04, 2016 1:35 pm

I think the statement at the bottom of the sales brochures " the manufacturer reserves the right to alter specification and/or prices without notification" says it all.

I am used to seeing a cable operated choke on a fulmar similar to yours, and Romac definitely do not list a cable for a fulmar choke ??

guess the design got changed early on, but no mention ever made of it because the FB concern and AMC itself were in decline, there is only a basic shared parts book for the fulmar , does this shed any light ?
JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Thu Aug 04, 2016 2:07 pm

The parts book has a list that states 375/37, and a picture that states 375/49! The picture shows adjusters for two cables. The banjo is shown with a feed straight out.
The handle bar set-up lists an air control lever and both cables. The cable part numbers are sequential suggesting that the choke was there from the start. The parts book is 1962 and states prices will increase 5% from May 62 so was in circulation before this.

I think the Fulmar had a 375/49 from the start and the special details that you stated for the 375/49 "Less air tube, rod controlled air valve" means less both items. Initially I took it to mean less the tube but including the rod control. The 375/37 has the rod control which could not work on a Fulmar. You can't get to it.

It would be useful to find out from members what their Fulmars have fitted.






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got to be !

Post  piston 197 on Thu Aug 04, 2016 2:19 pm

Steve, I think you have it nailed, guess they designed the Fulmar with the model 86 carb, then realised they could not get at the choke and altered the spec to include cable operation ? and never made the full correction in the parts book ?
JH
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Re: Fulmar trouble - fuelling?

Post  fulmar88 on Thu Aug 04, 2016 2:25 pm

Yes, and no-one told Romac either about the choke cable. So, my carb is probably the original which may also include the banjo feed in from the bottom (as other Fulmar pics suggest).

Steve.
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Re: Fulmar trouble - fuelling?

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