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Merlin 10D tickover issue

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Merlin 10D tickover issue

Post  trickydicky on Wed May 04, 2016 7:17 pm

Hello, I did post before about this but now need a bit more advice. The Bike starts fine but will not tickover at all. It either runs fast , very fast (really races) or stops. The throttle mechanism seems to be working fine and I have checked the needle movement. If I try to open the strangler a little it also stops. I did try making the mixture richer (raised needle) when the throttle is closed but it still stops.

As I only dismantled and reassembled the engine remaking all the joints (no parts repalcement), I am now wondering if the bearings and bronze seals are worn drawing in excess air but do not want to take it all apart again if there is something else I should check first. Does anyone have a good idea how to diagnose this problem? Help from the members would be appreciated.
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Re: Merlin 10D tickover issue

Post  Jack Clegg on Thu May 05, 2016 9:37 am

Sounds like an air leak. Carb manifold perhaps?
Also, the 10D has two crank oil seals doesn't it? No bronze seals I can recall on that motor. TTFN Jack
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Re: Merlin 10D tickover issue

Post  trickydicky on Thu May 05, 2016 10:09 am

Thank you.

Hi, no this engine does have two bronze seals and not rubber oil seals.

Rich
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seals

Post  piston 197 on Thu May 05, 2016 10:20 am

The 10D ( and the 6E) was made initially with the early type bronze washer seals and later with the rubber type

There should be no tickover on the 10D engine it should stop when the throttle is closed, but sounds like you have a slow running problem rather than a tick over problem ? and the mixture must be too weak if it will run with the strangle closed, but not open,needle has to be raised to richen the mixture, as you have a choke/strangler type filter I am assuming it is a single lever carb with the manually adjusted needle rather the cable operated needle ?
I had problems getting a happy medium with my 10D engine and ended up using one manifold from a Excelsior Talisman twin and an Amal 375 monobloc carb, runs a treat ticks over and is good throughout the rev range, not standard, but then again it is a James it is in , so what's the harm ?
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piston 197
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Re: Merlin 10D tickover issue

Post  trickydicky on Thu May 05, 2016 11:00 am

Thank you. Yes I would agree the problem is 'slow running' although I think there is plenty of fuel getting through but will check again. I'll keep screwing the needle up!

If that fails I'll strip down and replace the bronze bushes to be sure there is no air leaks and replace the bearings at the same time.

TD
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running fast

Post  piston 197 on Thu May 05, 2016 12:39 pm

Just sorted out a greeves that would not tick over and ran very fast when throttle was opened, the carb top was warped and missing the fibre washer, it was sucking air in through the carb top under the knurled ring. Changed the top and put a fibre washer under it ( all second hand bits off another carb) and problem sorted !

JH
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Re: Merlin 10D tickover issue

Post  trickydicky on Thu May 05, 2016 12:59 pm

I'll check that out too. Thnx
TD
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Carb top

Post  kerabo on Thu May 05, 2016 4:58 pm

So do all Villiers carbs have a fibre washer under the carb top?

Ken
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Carbs

Post  piston 197 on Thu May 05, 2016 5:04 pm

S22 S19 and S25 do it is not under the top it is between the top and the knurled ring, cannot comment on earlier brass bodied carbs, but the alloy ( mazac) bodied ones do .
JH
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Re: Merlin 10D tickover issue

Post  trickydicky on Thu May 05, 2016 8:38 pm

Hi I just checked and my carb does not by design have a fiber washer on the knurled ring.
TD
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Re: Merlin 10D tickover issue

Post  ScottT on Fri May 06, 2016 7:03 pm

John, there is no fibre washer on my S19, there is nothing in the manual suggesting a washer there.
My carb is currently at Villiers Services being reconditioned, when i fit the throttle cable on its return i'll see if they have fitted one
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carb top sealin washer

Post  piston 197 on Fri May 06, 2016 7:41 pm

I would think that probably there are more carbs out there without than with !, generally speaking if carb top, and knurled ring are in good order they will run fine without, but if there is any distortion then the air gets sucked in through there, I even once came across a bike that would not carburate correctly and found that it had a top with 2 holes in the top for throttle and choke cable, but no internal choke, putting bolt in the spare hole worked wonders !

JH
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Crankcase air leak Merlin 10D

Post  trickydicky on Sat Jun 04, 2016 6:48 pm

Hi,

I am pretty sure that the air leak is from the crankcase phosphor bronze crank seals and I note that the crankshaft moves up and down implying the bearings are worn . My plan is to replace the bearings and the seals (bushes) or, as I have a spare crankcase from a later model which takes the rubber seals I might swap it over as I am sure the rubber seals will be much better.

I have measured the bearing sizes but wondered if anyone can definitively tell me exactly what the sizes are. I measured using a vernier but allowing for temperature I can't decide what they should be and whether they are imperial or metric? Does anyone have a specification for the 10D crankshaft bearings and the oil seals?

Thanks TD
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trickydicky

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bearing sizes

Post  piston 197 on Sat Jun 04, 2016 7:55 pm

Merlin 1946/48 Villiers 9D engine
Drive side 2 off RLS 6/C3
Timing side 1 off RLS 6/C3
( Imperial size bearings)
gearbox 6204/C3
( metric bearing)

Merlin 1949/53 Villiers 10D engine
Drive side 2 off 6204/C3
timing side 2 off 6204/C3
Gearbox 1 off 6205/C3
(Metric Bearings)
the C3 spec is the amount of radial clearance required, any bearing supplier given these numbers should be able to supply the correct bearings of both size , quality and correct clearance

JH
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Re: Merlin 10D tickover issue

Post  trickydicky on Sat Jun 04, 2016 8:49 pm

Thankyou. that ties up nicely. Do you have the spec for the rubber seals too? By the way it is a D10 engine I have.

TD
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Merlin 10D tickover issue

Post  PeterW on Tue Oct 25, 2016 3:04 pm

Hi TD,

Just wondering if you ever got your problem sorted as Iíve got a very similar issue with my 10D engine?

Cheers,

PeterW
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Merlin Tickover issue

Post  trickydicky on Sat Oct 29, 2016 4:57 pm

Well I am not sure really. I have it running OK but it is not as smooth as I would like it. I readjusted points, timing, checking the setting against JH instruction and cross referencing with the manual.

To adjust the points I removed the contact wire and connected a test meter to identify when the points open. It is a bit fiddly and, does not seem to tie up exactly with the flywheel notch setting. I found the points opened earlier than the position where they should. I may be running slightly retarded but I have no doubt that a little more trial and error could get it running smoother but I'm in no hurry to tinker.

My biggest problem to resolve is a leaky gearbox and can't spot where it is coming from easily.
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Merlin Tickover Issue

Post  PeterW on Sat Oct 29, 2016 5:11 pm

Can be difficult to identify the exact source of a small leak sometimes.

Just wondering, did you replace the bronze crankshaft seals in the end?

Cheers,

PeterW
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Re: Merlin 10D tickover issue

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