Author Topic: Tank slapper and Amal 274s. (Read 15295 times)

Hampshirebiker · « **on:** 01 Sep 2015 at 15:35 »

I got the MK5 running reasonably and took it for a short test run. When I got up to about 25mph it developed an alarming tank slapper and I could not hold the handlebars. I felt the steering was generally heavy at the lower speeds and suspected a soft front tyre. Returning home in first, very gingerly, I checked the pressure - about 30psi. I know this is too high, but can't think this is the cause. A quick check of the head bearings indicated they were OK. I'll relieve some pressure, but I must try to find the cause. If it happens at a higher speed in the future, I'm in trouble.
Also I've convinced myself that the 274s are well past their best. Has anyone done a concentric conversion; obviously making adaptor flanges. Reliable starting and smooth running is my main requirement. I don't have either after several days playing about. Both brand new plugs have sooted very quickly - in a total of less than half an hours running.
Any help on either topic would be much appreciated, Dave.

oily bloke · « **Reply #1 on:** 01 Sep 2015 at 17:36 »

As a general rule (I am not a post war Douglas owner) Handlebar oscillation can be caused by the back of the bike as much as the front. Over tight headraces can cause the bike to weave but should not cause slap unless it is coupled with wear at the back (Swing arm, suspension,wheel bearings and bushes)
Check the wheel alignment as this can be contributory but not the cause.
I suspect you have more than one fault unless your rear wheel spindle is loose or the bearings have had the newness worn out of them.
Hope that helps.
Andy.

eddie · « **Reply #2 on:** 01 Sep 2015 at 18:44 »

Dave,
Check out the front wheel spindle nut. One of the lads that used to sprint a Douglas had problems with the forks flapping as he left the start line. That turned out to be the front wheel spindle nut being loose on the spindle, but not turning due to it being clamped in the leading link.
With regard to the carburation, modern unleaded petrol is notorious for drying out to a lacquer that easily blocks any of the small drillings. These blockages often result in poor starting and idling (and sooting up of the plugs) but don't normally affect the faster running. The back of the choke block has what looks like a blind drilling with 2 smaller holes entering from the sides, but there is also a very small hole (about 25 thou) in the bottom of the drilling - if this is blocked, there will be virtually no slow running adjustment. There is also a similar hole (about 30 thou) in the bottom of the bore of the carburettor - this is the outlet for the slow running mixture - and must also be cleaned out.
Hope some of this helps,
Regards,
Eddie.

Hampshirebiker · « **Reply #3 on:** 01 Sep 2015 at 19:23 »

Thank you gents for the advice. It's up on the lift tomorrow and a full check of the points suggested,
I did strip both carbs and put the bits through the ultrasonic cleaner. I also checked the carb blocks as you advised earlier Eddie. A fairly easy job to redo them as I could have missed one of the small orifices. The float needle seatings may need another look as one carb is prone to flooding; but occasionally.
Apart from the fact it doesn't start or run properly and nearly had me off, I'm very pleased with it.

AndyH · « **Reply #4 on:** 01 Sep 2015 at 22:52 »

Hi Dave

If you are getting occasional flooding it could well be sediment from the fuel tank that is finding it's way down to the float bowls. I had the same problem the fuel tap filter, it was just not
doing it's job. I replaced the fuel tap and also put 2 inline filters in the fuel lines. Could be undoing your carb cleaning work really quickly.

Andy

tck · « **Reply #5 on:** 02 Sep 2015 at 20:26 »

I too have had the ultrasonics and the eye piece routine on those poor carbs
I think they and the monkey metal they are made of are past redemption and are spoiling my Douglas
top of my search list for Netley a pare of 175 Honda carbs-its that or my matched set of Bowdens I must be getting desparate

Hampshirebiker · « **Reply #6 on:** 03 Sep 2015 at 10:33 »

I've checked the rear end & I can't find any movement or fault. I checked the front wheel as advised. The N/S bolt head was spanner loose & took about half a turn without murdering it. Like a pratt, I then checked the O/S nut (having loosened the pinch bolt). Having already tightened the bolt head this was tight. No bearing play or loosness anywhere that I could find.
The front wheel is spinning freely with just one slightly tight spot; presumably on the brake drum. There is some inbalance of the wheel as it always favours one resting place. I will wind a bit of solder wire round a spoke to balance it properly. There is a couple of mm run out on the rim & the tyre wall may be a little worse, but I'm probably nit picking now.
I'll get my lad to test it next as he's an experienced rider. I'm, shall we say, a bit rusty; to say the least.

dragonmk5 · « **Reply #7 on:** 10 Sep 2015 at 12:21 »

Well. my Mk4 has been rebuilt for some time now, but the worst aspect of this bike is the carbs. I have stripped, cleaned and reset them on numerous occasions, and it still runs like a bag of spanners. I'm going to have one more go at the strip down etc., and if that doesn't work, then I will have to look at replacing the carbs with modern units. Naturally I'll keep the Amals, so they won't be lost. Not too keen on spending much more on this bike, as I've rebuilt engine and gearbox, and to be honest, I don't know if this is the bike for me. Probably a bit unfair, as I know others run their Duggies all the time, but we'll see.

tck · « **Reply #8 on:** 10 Sep 2015 at 12:27 »

Did not find anything suitable at Netley I think its a case of getting VM Mikunis from Allens I am sure someone must have done this before but I have asked about settings and sizes here before and no-one is saying. I suppose a lot of people want originality at all costs but so long as its something that can be replaced in an hour or so and it makes the difference between really using the bike and not to me its a no brainer.

Hampshirebiker · « **Reply #9 on:** 10 Sep 2015 at 13:15 »

I'm seriously thinking of making a tubular manifold and using a single carb; as the Dragonfly. The plumbing side is no problem; just the mating flanges to the heads. A concentric would be better as it isn't quite so tall and space is a bit limited. I got the idea from the blown MK5 special posted recently.
An experienced friend of mine has suggested reducing the float levels a tad on the 274s may help with the running.

tck · « **Reply #10 on:** 10 Sep 2015 at 14:54 »

Like the dragon fly!

heaven forbid. someone may have a comparison of performance it must have suffered from that induction tract apart from the weight gain

eddie · « **Reply #11 on:** 10 Sep 2015 at 15:41 »

The biggest problem with the Dragonfly is the single carb combined with the Miller electrics. When I first got my Dragonfly, a long standing Club member asked if I had problems with the carb icing up. "No" said I. "You will tonight" came the reply. And sure enough, at the end of the dual carriageway into Petersfield I shut the throttle but the carb was frozen open. Have you ever tried killing a Dragonfly engine on full throttle? To kill the ignition, you have to kill the lights (all on one switch!). It don't 'arf get exciting!!!
I think I'll stick with the twin homebrewed 274's that have served me well for the last 20 years!

Eddie.

dragonmk5 · « **Reply #12 on:** 10 Sep 2015 at 16:27 »

Stripped carbs, paying careful attention to airways etc.,bodies cleaned and reassembled.
Started up and, lo and behold, it's STILL running poorly. Last throw of the dice tomorrow will be to try using the colourtune to see if it improves matters. Not holding my breath!

Hampshirebiker · « **Reply #13 on:** 10 Sep 2015 at 16:54 »

Good idea with the Colortune. I've still got mine and I'll give it a try.
P.S. Eddie, did you get as far as the Half Moon car park before it finally stopped?

eddie · « **Reply #14 on:** 10 Sep 2015 at 17:06 »

dragonmk5,
Are you sure it is a problem with carburation? A weak spark can cause rough running, and often gives similar symptoms to a rich mixture.
Dave,
Yes, I did get it stopped pretty quickly - Dragonfly brakes DO work, especially if you have attained the necessary level of panic!!

Regards,
Eddie.

dragonmk5 · « **Reply #15 on:** 10 Sep 2015 at 17:24 »

I did wonder about the magneto / spark, so today I used a "detector " on each plug, and the spark seemed to be regular and quite strong. I set the mixture screws at 1 1/2 turns out as a starting point.
Bike starts easil from cold, but when hot, I have to tickle the carbs to get it going again.
one of the floats has had the needle soldered in place, but it's about the same as the other one re needle height. The slides are badly worn and I think the bodies are simply worn out, as the threads on the mixture screw are extremely sloppy. I'll try again tomorrow.
Thanks for the help gentlemen ; all advice and comments gratefully received.

graeme · « **Reply #16 on:** 10 Sep 2015 at 23:49 »

I think you may have said it all with " The slides are badly worn and I think the bodies are simply worn out". When I first bought my T160 Trident 32 years ago, I could get no sense whatsoever out of the running, until I realised that the Concentric carby bodies and slides were worn out - after under 10,000 miles from new mind you! I had the bodies machined round again, and stainless steel sleeves fitted on the slides. Result - I could get some sense out of the carburation. They have been fine for the subsequent 60,000 miles the bike has covered. I've had to replace the needles and needle jet a couple of times as they wore, have fitted nylon tipped float needles and upped the main jet to suit the non-standard mufflers now fitted, but the bodies and slides are still working fine.

I suggest you might consider getting your carbys refurbished - there must be people who do this in the UK.

Another thing I had to do after a lay-up of the bike once, and couldn't get it to idle. I stripped down the carbys and put them in a large saucepan of boiling water with a tablespoon of dishwasher powder in it, boiled them for a couple of hours - this cleans out any internal passageways. Did the trick, idling could be set perfectly after this.

Cheers, Graeme

dragonmk5 · « **Reply #17 on:** 11 Sep 2015 at 19:38 »

No luck today, so I'm going to look at the Mikunis etc.. Not sure of the size yet, but I'll start looking at carbs for a 175 / 200cc engine.
While on subject of fuel, on eBay I saw someone selling o rings as an alternative to cork for the Ewart tap. Looked quite a good option.

Hampshirebiker · « **Reply #18 on:** 11 Sep 2015 at 21:51 »

Dragon, noting the soldered float needle. The extra weight of the solder may alter the fuel level. The float will not be so boyant.

dragonmk5 · « **Reply #19 on:** 12 Sep 2015 at 09:07 »

Thanks re comment about soldered float. It's possible to buy certain parts for these carbs, but the cost almost equals the price of a modern carb; and I haven't found a source to bore the bodies and supply oversize slides yet. If and when I do, I reckon it will still be more cost effective to fit modern units, so I'm going to do some homework on that front. While at the Langford show a while ago, Dave L mentioned that we might have new bodies in the spares section, so I will ring on Monday to get a price.

Neville Heath · « **Reply #20 on:** 23 Sep 2015 at 18:55 »

Are you sure you put the shim on the spindle? part no 21 plate 26. If not the wheel will remain loose even though the nut is tight. This could give you a wobble!
Neville

Hampshirebiker · « **Reply #21 on:** 24 Sep 2015 at 14:03 »

Thanks Neville. All I can see is a large washer behind the head of the hollow nut (?). Is this the spacer, as I.m a bit confused with the relationship between parts 9&20 in the book. I'll post a photo if I can, but didn't have much luck last time.
Should I take the spindle etc. out to check all is there?
Dave.

eddie · « **Reply #22 on:** 24 Sep 2015 at 17:11 »

Dave,
Item 9 is the sleeve that carries the 2 front wheel bearings. The wheel spindle goes through the sleeve and the nut (item 20) tightens against the sleeve - with a spacer (item 21) if necessary. Now, with the pinch bolt slackened, the nut should tighten against the sleeve with some clearance between the head of the nut and the fork link (the washer shown in your photo should not be there). The idea is that the whole assembly should clamp up to the link on the brakedrum side. With this achieved, the offside link should be free to self align before nipping up the pinch bolt. The whole suspension should then move as one solid unit.
When we were involved with the Club's spares scheme, we found that there were several lengths of nut (item 20), so I guess that is the reason for making several thickness of spacer available.
Hope this makes things a little clearer.
Regards,
Eddie.

Hampshirebiker · « **Reply #23 on:** 24 Sep 2015 at 18:06 »

Thanks again Eddie. As time's not an issue for me, I might do a bit of dismantling to see (with your write up) what makes it all tick.

dragonmk5 · « **Reply #24 on:** 25 Sep 2015 at 08:43 »

Just an update re the carbs, over a week ago I emailed Allen's to see what they could suggest but have not received a reply. I reckon they don't want to comment in case of problems, so it would be a matter of me specifying the carbs I want, which they would then supply. As I'm not sure what I need, I've put the bike to bed for now!

tck · « **Reply #25 on:** 25 Sep 2015 at 12:56 »

They took a few weeks to come back to me on my Comet request
if you get a VM from them of the correct bore I have found I only needed to change one pilot jet size it would seem that the Mikuni jets cover a narrower range than the old Amals did.

Hampshirebiker · « **Reply #26 on:** 28 Sep 2015 at 14:11 »

Back to the engine; which is my main priority. I dropped the fuel levels about 1.5-2mm. As always ran the lamp over the plugs & wire brushed. Tickled & first kick start. Fast idled for a minute or two; with a few blips of the throttle. Then readjusted the pilots. Both pilot screws now had a good effect on the running. Reset the stops & turned off the engine. The plugs were no longer sooted, but still discoloured.
Tried to restart & not even a cough. With hindsight this has been my trouble all the way through. Start off cold, clean the plugs, a good flood & away it goes. Just try to restart & nothing. I've rechecked the points & connecting a strobe lamp shows a very weak spark. This may be an unfair test on a magneto; I wouldn't know.
I'm starting to think a weak magneto now. Assuming there isn't a home test I can do, I'd better get it checked professionaly. Any further thoughts would be greatfully received. No rush as I've given up on the idea of riding it seriously this year. A bike that won't restart is not worth riding.

oily bloke · « **Reply #27 on:** 28 Sep 2015 at 15:34 »

A good mag should have a nice blue spark at almost any speed.
I have had a couple of mags done over the last few years and you can turn them over by hand and a big fat spark ensues.
If the spark is weak or orange, assuming plugs, caps, leads and pick ups are ok, implies help is needed.
Andy

eddie · « **Reply #28 on:** 28 Sep 2015 at 15:46 »

Dave,
If your mag only gives a weak spark, it could be the windings or just the condenser packing up. Quite often deteriorating mags will start an engine from cold, but then refuse once any heat is generated. Before removing your mag, you could check whether it is the condenser failing by wiring a condenser from a distributor to the cutout lead - if there is an improvement, then the internal condenser is at fault.
Regards,
Eddie.

Hampshirebiker · « **Reply #29 on:** 29 Sep 2015 at 14:45 »

I've now gone as far as I can go with the starting. I fitted an external condenser & cleaned the pick up rotor in the mag. Fuel levels also returned to standard. Clean the plugs & it starts cold (getting more difficult). Hot starting - not even a cough.
Any recomendations for someone to check (& refurb if reqd.) the magneto. I prefer someone in the south. I always like to meet & have a chat with whoever.
Thanks in anticipation, Dave.
P.S. I've convinced myself that I can live with the carbs, so long as I can bl**dy well start the thing.

eddie · « **Reply #30 on:** 29 Sep 2015 at 17:56 »

Dave,
I have always found Paul Lydford of APL Magnetos at Shaftsbury to be good. He's done quite a few mags for our sprint Duggies and they have proved to be extremely reliable.
Regards,
Eddie.

Hampshirebiker · « **Reply #31 on:** 30 Sep 2015 at 15:21 »

Sorry to see-saw this topic about, but back to the front spindle. The eronius washer in the photo was an "O" ring, so probably of no consequence. I have removed the bolt, spindle nut & shim (19/20/21) - see photo. The shim is 0.18" thick so thicker than listed. There was no washer (44), but I can find one if size is not critical. I assume it goes directly under the head of the spindle bolt.
Left in situ through the wheel is a plain sleeve, which seems to be divided at the face of the brake plate (a bush for the N/S link?). What had thrown me was the hexagon head shown on the hollow spindle (9) in the parts book, but I see they list a plain item also.
If all is OK with what I have, I'll just put it back together with a washer on the N/S.
Thanks, Dave.