Author Topic: Exhaust to Cyl. Head / Ignition  (Read 737 times)

Offline Zander

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Exhaust to Cyl. Head / Ignition
« on: 15.03. 2017 20:05 »
Having refitted all bits that were removed during the course of " getting to know my new bike", I started it and noticed that the near side pipe had blown off its seating in the cyl. head. Also I note that both silencers (!) are loose on the downpipes, despite the clamps being fully tightened, so is it customary to use exhaust paste?  I've never used it on a bike before, but I suppose there's always a first time!
Further to my running problem posted in the carb section, I set the ignition timing to 11/32 BTDC, fully advanced.  I've seen publications which state 9/32 or 5/16, but I think 11/32 is correct.  Looks like I'll need to check it tomorrow - I might even rig up a timing disc! Onwards and ( I hope) Upwards *work*
'59 GF

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Re: Exhaust to Cyl. Head / Ignition
« Reply #1 on: 16.03. 2017 04:21 »
G'day Zander.
Ill fitting pipes can be a bugga. You might be able to tweak the bracket to hold the pipe in better and/or get the pipe expanded (any car exhaust shop can do that) to fit better. I do use exhaust cement for the best seal. Same at the silencer end or make a sleeve to go over the pipe and into the silencer.
Timing depends on the fuel you use. 11/32 is a good starting point. Too advanced she'll ping, too retarded she'll overheat.
Cheers
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Muskys Plunger A7

Offline Zander

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Re: Exhaust to Cyl. Head / Ignition
« Reply #2 on: 16.03. 2017 08:28 »
Thanks, muskrat.  I've sorted out some thin steel sheet to make the collars for the silencers, and will explore enlarging the pipe, but first I'll see if I can adjust the bracket without messing it up. Regarding the timing, I think I'll take a short ride to see how it runs before I mess with that.
 *wink2*
'59 GF

Online JulianS

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Re: Exhaust to Cyl. Head / Ignition
« Reply #3 on: 16.03. 2017 10:16 »
PTFE tape around pipe will improve fit in the head .

I think part of the problem is that the original pipes were 1 1/2 inch OD and recent pipes are 38 mm od.

If its really loose add some exhaust sealant paste. It come out easy enough when dismantling.

I have been using it for years.

BSA recommended paste for fitting the 2 into 1 exhaust so if it was good enough for them its good enough for me.


Offline terryg

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Re: Exhaust to Cyl. Head / Ignition
« Reply #4 on: 16.03. 2017 11:06 »
As an alternative, use the forum search on 'silicone exhaust' and you'll find a number of recommendations to use silicone sealant on the pipes.  Sounds a little odd at first, perhaps, but silicone is good for the temperature and not too difficult to clean off when necessary.
It won't replace the shims if you need those but it should make it easier to get a seal.
Terry
'57 'SR', '59 SR, '63 RGS

Offline Zander

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Re: Exhaust to Cyl. Head / Ignition
« Reply #5 on: 16.03. 2017 11:51 »
The pipes are indeed 1.5" diameter. I happen to have some exhaust sealant left over from fitting a down pipe to a mini, so I might try that first, providing it hasn't gone rock hard like most of my tubes of sealants and silicone have!
'59 GF

Offline chaterlea25

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Re: Exhaust to Cyl. Head / Ignition
« Reply #6 on: 17.03. 2017 11:30 »
Hi All,
 *warn* *warn* *warn*
Be very careful applying exhaust paste,
Make sure none goes in past the pipe to cause a "lump" in the port
A lump of exhaust paste in the port will cause heat reflection back to the exhaust valve and the valve head can snap off the stem with disastrous results *problem* *angry*

I have seen this happen more than once *sad2*
John
1961 Super Rocket
1963 RGS (ongoing)

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Re: Exhaust to Cyl. Head / Ignition
« Reply #7 on: 17.03. 2017 11:50 »
Good point.

I apply to the pipe and not the port so excess gets pushed out not in.

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Re: Exhaust to Cyl. Head / Ignition
« Reply #8 on: 17.03. 2017 19:39 »
Good point John.
I only apply to the pipe but now I wonder if this was the cause of my Cafe's catastrophic failure *ex*.
Cheers  *sad*
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Offline coater87

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Re: Exhaust to Cyl. Head / Ignition
« Reply #9 on: 17.03. 2017 21:36 »
 That and 14000 RPMs might have been the cause..... ;)
Central Wisconsin in the U.S.

Offline chaterlea25

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Re: Exhaust to Cyl. Head / Ignition
« Reply #10 on: 17.03. 2017 22:16 »
Hi Muskie,
Quote
That and 14000 RPMs might have been the cause..... ;)

Hmmmmm!!!! *sarcastic*


*dunno2*
John
1961 Super Rocket
1963 RGS (ongoing)