ES2 performance

Andy, I'm not surprised. The main jet should be 270 and while you are about it, the slide should be No 4.

Hope these changes improve things significantly.

PS: 276? I was working on a 376 or even a Mk1 consentric.

I would have expected the engine to reach max revs in both second and third gears. Then drop a fair amount in top. The figures suggested to me that this bike was slightly overgeared and under carb'd. Talking with some of our older and wiser members with big singles. They say that, back in the 50s, cruising at 55mph was the norm on a bike such as the ES2 as the poor roads surfaces and iffy bike suspension did not help to achieve faster speeds that were safe.

Checkout the attached info about sprockets and carbs. If I was trying to get more go out of an old ES2 I would be definitely fitting the 376 carb and possibly changing the gearing.

Previously andy_marks wrote:

I've been playing with my ES2 today as I wasn't happy with the performance; it went flat at about 55 in top and wouldnât pull past this speed. After a conversation with Mike Pemberton I checked and altered my valve timing, I now have the inlet opening 27BTDC and the exhaust closing 32ATDC. I know the exhaust is a little later than ideal but itâs as close as I can get it with the standard cams and gears. Ignition timing is 5/8BTDC fully advanced.

Based on one of Mikeâs articles in Roadholder it should be capable of 53 in 2nd, 71 in 3rd and 82 in top. Now I can't really afford to rebuild the engine again so I was being a little sympathetic, but I still got about 50 in second and about 65 in 3rd. All was going well until I changed into top, it just sat at 65 and offered no further acceleration, I can slow down to about 30 and accelerate back up to 65 without changing down, so its pulling top gear with no trouble at the lower revs.

A few sums and the top speeds in each gear equate to about the following RPM:

50 in second - 4760RPM

65 in third - 4230RPM

65 in top - 3496RPM

I'd expect it to rev a little less in each gear as you go up, but why the sudden lack of acceleration in top?

I have a 21T engine sprocket which is one above standard, all the other sprockets are as original.

It's on a pre-monoblock 276 carb with a 160 main jet. I played with this a few weeks ago and found that to be the best size, maybe I need another look now I have altered other things?

I have a 16H piston in it giving about 8.2:1 compression.

I know the valves seats are quite badly recessed up into the head and I plan to take the head off over the winter and get new valve seats fitted, but would that make this big a difference?

Anything else I have overlooked? Anyone experienced these symptoms before and able to offer any help? My last trip round the block to try it out saw the speedo tick over the 3000 miles since Iâve had the bike on the road (about 18months), so Iâd like to get it sorted now, Iâm getting a little tired of seeing this one up on the bench!

Thanks in anticipation

Andy hi andy,had same trouble with bsa b1 ages ago,did everything like you and decided motot was very tired,began strip to find bore very good,checked head and found exhuast valve to be quarter inch shorter than standed,fitted new terry springs and refurbished head and the bike goes better than ever,also,go down one tooth from standard on engine sprocket and go up one on gearbox ,no affect really on top speed but you will have much perkier accelleration especially in wind and up hills,regards,bruce,australia.p.s.my 16H norton is in march copy of roadholder.

Go back to a 20T engine sprocket. Even over-gearing by 5% can result in the bike being no faster in top than in 3rd. You may just be surprised...

The 276, and the the monoblock used the same type of jets, and were the same bore. There is a vast difference between 160, and the 270 jets recommended for the monoblock. Has a typo crept in somewhere? In the 50's, before I got a Dominator 88, I cruised at over 60 m.p.h. on a rigid rear B31. The roads were probably better then than today, and, there was far less traffic (and no maximum speed limit on unrestricted roads). 55 m.p.h. cruising speed Phil, who have you been talking to? I used to average over 50 m.p.h., between Blackpool and S.E. London (before there were any motorways).

Are you sure about the jets John? Quite different in my similarly equipped bikes. My MSS Velo has a sweet spot at 58mph with plenty more if required - an ES2 should be similar in performance. It can take a fair bit of trial and error to get the carb set up properly and that can make a remarkable difference.

Your overgeared. Also if the valves are sunk this will not help. If you have 23bhp I would be suprised. If you want to go faster and want a Norton go for a twin. You will spend a lot of money making a single ES2 keep up with a twin Andy.

Jubilee should be no problem!

My poor man's Manx (59 ES2 in a wideline) runs a 22 tooth engine sprocket and 20 tooth gearbox sprocket.

Pulls away fine though acceleration is slightly sluggish but 60 mph cruising is very relaxed with plenty more on tap. I use a 30mmMk 1 Amal, though I have seen these machines with 34mmMk2's.

3 1/2 slide and currently 230 main jet with plug a perfect light brown colour. Seems to me that the bigger the carb the smaller the main jet and lower number slide? Sounds logical at least. Oh, andGoldstar type exhaust system too!

Sorry for the delay, Andy. Other tan the high gearing, Goldstar pipes and 30mm Mk 1 Amal, that's about it.

The bore was on +60 and well worn, I tried it with new rings but it was too far gone and using oil. A mate made me a sleeve and I went for an AP piston (79mm) from RGM. A good quality piston but I should have realised it was a bit heavier than original. Even so it is reasonably smooth, no real vibration but slightly lumpy. I still like it.

My ES2 on the other hand is 530cc using a 28mm Mk 1 Amal. The gearbox sprocket is 20 tooth but otherwise everything is standard, as on the PMM. They both go well on BP Ultimate and a bit of RedX lead replacement and a dash of castor, just for the aroma!!!!!!

Previously Andy Marks wrote:

Just as an update - After saying I was going to leave it alone untill the winter, I had a spare afternoon yesterday so decided to try putting the brooklands can from my Inter on the ES2 to test the idea that the standard exhaust could be choking it. I went for a quick test ride and although I have no more top speed, I had a lot more low down 'grunt'. I went back up to the 21T engine sprocket and again, its not really any faster but it is pulling better lower down the rev range. It also made it run weaker so I have gone up a main jet size (I have no idea what all this means in the grand scheme of things, but its obviously made a difference)

Its more comfortable at 55-60mph now (appart from the noise!) So now I really will leave it alone until the winter when I plan to fit a bigger carb, open up the inlet to suit and have the valve seats done. I am also tempted to splash out on a set of Mike Pembertons cams just to really get the best out of it.

Thanks again for the advice

Andy

Hi Andy .... Recognising that this is a fairly old thread, I'm just wondering how it all ended? Did the head work get performance to where it should be?

Ta

Andy

Just had the Model 18 for a few weeks now. Good compression, starts first kick, runs and sounds lovely, but definitely not quite right as it just about hits 55 mph and feels like it has more torque but no more power than my Tiger Cub. Ignition timing is good and valve timing appears good, although I'm measuring in terms of distance bTDC rather than with a degree wheel. But I'm sure they're not far out. I've put new petrol in - no idea how old it was - and new spark plug goes in tomorrow. I'll then see how the plug looks during a "fast" run. If those don't solve it then a carb strip down seems to be the next step but the main jet seemed clean when I undid it yesterday.

Fingers crossed.

Phil