Author Topic: XBR 500 with no compression  (Read 1208 times)

stanyon

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XBR 500 with no compression
« on: August 07, 2006, 07:13:37 PM »
Hi,
I have just joined the clan with a xbr.  bought as a non runner that has been sitting about for a while.  It has very little or no compression and i want to pick your collective brains as to why ?  I guess I'll have to pull the head off and see but is there anything I should check first ?  Also, where can I get a manual for the bike.  Its an 86 model  thanks in anticipation Brian

002

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Re: XBR 500 with no compression
« Reply #1 on: August 07, 2006, 09:53:42 PM »
Check valve clearances first !
Assuming it was a good runner to start with !

But I expect its sticky rings.They gum up after a period of inactivity !

What you can do is to remove spark plug and poor in sone WD40 or similar and let it soak.
Spin it over like Bu@@ery on the Leccy foot or kick starter.
Possibly wont work first time but keep at it.
It will eventualy build up and then start and be right as rain.

I had one and GC did,that once in a blue moon do it over night for some strange reason.
My Enfield has stood for a while that has done it.
Eventually got it going and now can stand on the kick start lever without turning it over,compression is back to square one.No problem.
Nothing to worry about really.

Jethro
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Lee Enfield
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guest7

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Re: XBR 500 with no compression
« Reply #2 on: August 07, 2006, 10:34:02 PM »
If I left any of my XBRs for more than a week they all did it. Basically you need to keep turning it over until the rings free off, and yes you can still do this on just the kickstart if you have to.

I hope it's not more serious than that, but given their habit of losing compression I'd try to keep kicking it over first.

GC

GB500nz

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and then there's the decompressor
« Reply #3 on: August 08, 2006, 08:52:25 AM »
How can you stand on the kickstart? All my GBs could be kickstarted by any energetic 11-year-old girl. There's a decompressor connected to the kicker. If it gets stuck, of course, there's no compression. Or are XBRs that different?

guest18

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Re: XBR 500 with no compression
« Reply #4 on: August 08, 2006, 01:05:52 PM »

My Enfield has stood for a while that has done it.
Eventually got it going and now can stand on the kick start lever without turning it over,
Jethro

"Are XBR's that different"... they are if they're Enfields ;)
No offence GB500NZ!!

(now I'd better be careful what I say!! :-o )

SteveC#222

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Re: XBR 500 with no compression
« Reply #5 on: August 08, 2006, 05:45:17 PM »
My XBR has done this once or twice, in fact it did it on Saturday - the first time I've struck it up since the annual rally where it did the 600 mile round trip without missing a beat! No joy on the leccy start , no proper compression on the kick start. After about 5 minutes of kicking it started with an almighty bang which scared the crap out of next doors pigeons!! I since done the valve clearances which were only slighty out. As GC says, I think it's probably sticking rings.
Growing old is inevitable, growing up is optional!

002

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Re: XBR 500 with no compression
« Reply #6 on: August 08, 2006, 09:24:42 PM »
Had a Triumph 955 Sprint ST do it recently aswell.

Just keep spinning it over and going back to it now and then during the day and it started.

As I said Sticky Rings !   So dont let them stand for too long otherwise you too will have a Sticky Ring !


Jethro
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Martini-Greener GP
Lee Enfield
ELG

squirrelciv

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Re: XBR 500 with no compression
« Reply #7 on: August 09, 2006, 06:03:22 AM »
Could this account for something that happened to Dolly a year or two ago?

She'd been laid up for about 3 weeks while I was off work and painted the exhausts (total waste of time BTW) When I fired her up, she was reluctant to start, and when she did, she ran very very hot for about a minute. Hot enough infact to get the exhausts cherry red, and burn off all the heat proof paint I'd just put on :-X Never done that before and never done it since, a total mystery to me. So could that have been a sticky ring leading to a weak mixture???
Live long, live well, live happy

guest27

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Re: XBR 500 with no compression
« Reply #8 on: August 09, 2006, 03:37:23 PM »
First off - welcome to this happy band.

Secondly I know less about XBRs than I do about solving middle east relations.  However.  Was the bike running and is there any information as to why it stopped running?  Just wondering if it were something like a bent valve, then could we not be increasing any damage by kicking it over loads?  Would it be an option to run a little engine oli down the plughole to produce a very temporary seal.  If there is compression for a kick or two with oil - it is gas passing the piston, if there is not then it is gas getting out from else where?  Maybe I am being a bit of a worryguts, but I used to have a Superdream that "lacked" compression and would not start unless you jumped up and down loads on the kick / ran the battery down on the lekky start.  Thought it was knackered bores / rings.  turned out to be a couple of valves that were approaching time expired and were splitting.  Eventually one broke and dropped into the engine, the con rod did nto like this intrusion and came out to make its feelings known...

However having never even ridden an XBR let alone pulled one apart I would nto listen to me but would listen to others...

R

stanyon

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Re: XBR 500 with no compression
« Reply #9 on: August 11, 2006, 06:36:36 AM »
Thanks for all the advice.  I have checked the valve clearances and found one to be about 1/2 inch.  I thought that might be a bent valve so I pulled off the cam cover (you all know where this is going)  one of the exhaust cams had eaten a follower!  so now I'm looking for replacement parts.  SEP will re profile the cam and followers for about £140 and have suggested a fast road profile.  I,m delving deeper into the lump because the cam problem wouldn't have caused low compression.  I have no history of this bike.  The guy I bought it from had never had it running, although he did fit new tyres and a battery, just hope I get a chance to wear them out.   Brian

guest18

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Re: XBR 500 with no compression
« Reply #10 on: August 11, 2006, 03:59:57 PM »
Yup, sadly XBR's will do that. I got a replacement cam and followers from David Silver and I would say it's worth phoning them for the cost of oe parts just in case there is a significant saving...
I would also personally not bother dissassembling further as 9 chances out of 10 the lack of compression is sticky rings, mine at the moment has stuff all compression through not running for a while but I know as soon as I crank it over for a while and it starts the compression will return almost immediately.

Your bike right enough so do what you want ;-) Personally though I'd fix the top end then see if/how she runs before doing anything else.

Good luck!
Smudge

ps. If you have cause to take the head off then a pound to a penny you'll find a small crack in it, DON'T WORRY(!) firstly they all do that and secondly it makes no difference to how they run as far as anyone can tell :-)

#1

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Re: XBR 500 with no compression
« Reply #11 on: August 16, 2006, 09:17:40 AM »
to clarify on the crack issue, there will almost certainly be a crac k coming from the sprk plug hole. Don't worry about it, "they all do that squire"

GC

Brian Stanyon

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Re: XBR 500 with no compression
« Reply #12 on: November 05, 2006, 10:55:42 PM »
a quick update
I pulled the head off and one of the exhaust valves was holding off the seat.  i have cleaned up the valves and put it all together and it runs nice.  I took it round the block (read private road) and the spedo doesnt work.  looks like bits are missing from the spedo drive another little problem before the MOT.  I knew I should have bought a runner !

bullet350

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Re: XBR 500 with no compression
« Reply #13 on: November 07, 2006, 12:38:59 PM »
speedo's don't get tested in the mot.
my old bsa speedo gave up and a new one was £150!!

£15 universal mini speedo connected to the outer of the speedo cable got it an mot.
the inner bit of speedo cable had to be removed as the new speedo was metric. probably fairly illegal, but as long as the speedo reads zero when stopped the police can't tell.

of course 350 bsa's don't bother speed cameras.

bullet350.

Richard 003

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Re: XBR 500 with no compression
« Reply #14 on: November 17, 2006, 10:55:25 PM »
a quick update
I pulled the head off and one of the exhaust valves was holding off the seat.  i have cleaned up the valves and put it all together and it runs nice.  I took it round the block (read private road) and the spedo doesnt work.  looks like bits are missing from the spedo drive another little problem before the MOT.  I knew I should have bought a runner !

Yay! Success. Excellent. Speedo, schmeedo, you can always get another speedo. Not just a broken cable?