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xs500 not starting (driving me crazy)

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Jay2903
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PostPosted: 15:28 - 15 Nov 2017    Post subject: xs500 not starting (driving me crazy) Reply with quote

Hey guys

I've been working on this one for a while and it won't start now. I put a new battery in yesterday and the plugs, plug caps, condenser and ignition coils are new. I've also Checked points. The spark seems to be ok. The carbs have had some new bits also.

Theres a few things i think it might be. Both carbs were leaking slightly the other day, i adjusted the carb floats which stopped it.

Second thing, i have removed the original airbox and replaced with pod filters. Maybe the mixture it too off to start.

Final thing, once I've tried to start it for a bit, when i pull the plugs the right one is a bit wet but the left one is dry.

As always, any help greatly appreciated.
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Chris45
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PostPosted: 15:45 - 15 Nov 2017    Post subject: Reply with quote

So the plugs are definately sparking? And the timing is spot on? I would go back a few steps. Try setting it up with the standard air intake filter etc. Double check the float bowls again for ANY leaks, and also check your intake between manifold and carbs for air leaks etc. Wet plugs just tell us petrol is getting into the cylinder, a dry plug on the otherhand????

Hope this helps.
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Jay2903
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PostPosted: 17:01 - 15 Nov 2017    Post subject: Reply with quote

Chris45 wrote:
So the plugs are definately sparking? And the timing is spot on? I would go back a few steps. Try setting it up with the standard air intake filter etc. Double check the float bowls again for ANY leaks, and also check your intake between manifold and carbs for air leaks etc. Wet plugs just tell us petrol is getting into the cylinder, a dry plug on the otherhand????

Hope this helps.


Cheers

Definetly sparking (kicked it with the plugs resting on the head). Timing is fine (checked it about a month ago). i can't put the air box back on, bit of a long story why. There aren't any fuel or air leaks.
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Jay2903
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PostPosted: 17:42 - 15 Nov 2017    Post subject: Reply with quote

Is it possible messing with the carb float has caused the left to not get fuel now ?
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Suntan Sid
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PostPosted: 10:58 - 16 Nov 2017    Post subject: Reply with quote

Carbs scrupulously clean?
Are the the pilot jets set correctly?
Are you absolutely sure the diaphragms are air tight?
Have you changed the jetting to compensate for the lack of air box?

Working on the premise that a lot fuelling problems turn out to be electrical problems, have you actual tested all the components?
Have you renewed the condenser for the points?

Sorry for stating the obvious but, kill switch and choke, are they in the correct positions when you try and start the bike?
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Chris45
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PostPosted: 18:02 - 16 Nov 2017    Post subject: Reply with quote

Quote:
Sorry for stating the obvious but, kill switch and choke, are they in the correct positions when you try and start the bike?


Agree with all the above, it really is a case of going back through everything. I know it's really frustrating, been there so many times over the years with all sorts of problems, mostly electrical. Anyway getting back to you, read what Suntan Sid has advised, then read my advice again. Am certain your problem lies on the intake side. Good luck, plenty of tea helps too!
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bugeye_bob
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PostPosted: 19:39 - 16 Nov 2017    Post subject: Reply with quote

Random answer, does the bike have a reed valve? is that fine and installed correctly, it`s that age that could, and I had the same issues many moons ago that was a reed valve issue,
it had spark and fuel, we bumped and bumped it, still nothing.
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Suntan Sid
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PostPosted: 20:53 - 16 Nov 2017    Post subject: Reply with quote

It's a 4 stroke, with CV carbs! Rolling Eyes
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Stoker
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PostPosted: 22:35 - 16 Nov 2017    Post subject: Reply with quote

bugeye_bob wrote:
Random answer, does the bike have a reed valve? is that fine and installed correctly, it`s that age that could, and I had the same issues many moons ago that was a reed valve issue,
it had spark and fuel, we bumped and bumped it, still nothing.


Never heard of an inline 2 cylinder four stroke engine using reed valves before, perhaps that's the problem.

Edit, Dammit Sid!
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Stoker
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PostPosted: 22:44 - 16 Nov 2017    Post subject: Reply with quote

Ok, so what exactly has changed since it was last running, and how exactly was it running then?

You seem to have replaced/changed a few things in your original post, can you talk us through your thought process?

Have you, for example been trying to "cafe racer" it?


Last edited by Stoker on 22:46 - 16 Nov 2017; edited 1 time in total
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V2
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PostPosted: 22:45 - 16 Nov 2017    Post subject: Reply with quote

To help confirm or rule out possible fuelling issues I usually see if it will start using 'easy start' If it starts or fires on that then look into the carbs/fuel delivery side of things, If it wont start on that then there may well be another problem to sort out first!
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Jay2903
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PostPosted: 23:33 - 16 Nov 2017    Post subject: Reply with quote

Cheers for the help guys.

It was the float that I adjusted wrong. Looking at the fuel lines it looked like fuel was flowing into both carbs but when I opened the left one there was barely any in there. I adjusted it then stuck it back on and it started...

The next day I went to start it again and it would only fire on the left cylinder. The plugs were fine yesterday but now the right one isn't working (only a month old). I'll be picking up a new one tomorrow and the adjusting the mixture.
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Jay2903
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PostPosted: 05:27 - 18 Nov 2017    Post subject: Reply with quote

So I picked up a new plug and stuck it in. It struggled to start but eventually did but was only firing on the right. I unscrewed the pilot on the left and it started to kick in. It would idle at about 1.5 k but when I gave it a little rev past 2k it it wouldnt go back down to idle . It instead would climb up and up past 6k.
What should I be adjusting ?
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jaffa90
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PostPosted: 10:57 - 18 Nov 2017    Post subject: Reply with quote

Sounds like the fuel levels are varying in the carb /s.
Providing the carb slides are free to control.
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Bru
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PostPosted: 16:49 - 18 Nov 2017    Post subject: Reply with quote

High-hanging revs suggest air could be getting in downstream of the carb. Can you check that the rubbers are fitting tightly over the carb and inlet mouths?

Another way to check this is, (if) the engine is running, spray some damp/easy-start spray (or even WD40) over the joint. If the revs pick up, then that's the problem.
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Jay2903
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PostPosted: 14:24 - 19 Nov 2017    Post subject: Reply with quote

Bru wrote:
High-hanging revs suggest air could be getting in downstream of the carb. Can you check that the rubbers are fitting tightly over the carb and inlet mouths?

Another way to check this is, (if) the engine is running, spray some damp/easy-start spray (or even WD40) over the joint. If the revs pick up, then that's the problem.


I checked the rubbers, they fit tightly over the mouths. I tried the wd 40, the revs didn't increase at all.
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Jay2903
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PostPosted: 14:31 - 19 Nov 2017    Post subject: Reply with quote

I tried it again today, it started up fine. Both cylinders seem to be working equally. It idles at around 1.7k but when i rev it, it doesn't return to idle. It also doesn't run without the choke on.
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Jay2903
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PostPosted: 14:32 - 19 Nov 2017    Post subject: Reply with quote

jaffa90 wrote:
Sounds like the fuel levels are varying in the carb /s.
Providing the carb slides are free to control.


What do you mean by this ?
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nowhere.elysium
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PostPosted: 15:00 - 19 Nov 2017    Post subject: Reply with quote

Jay2903 wrote:
I tried it again today, it started up fine. Both cylinders seem to be working equally. It idles at around 1.7k but when i rev it, it doesn't return to idle. It also doesn't run without the choke on.

Air leak?
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Jay2903
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PostPosted: 15:19 - 19 Nov 2017    Post subject: Reply with quote

nowhere.elysium wrote:
Jay2903 wrote:
I tried it again today, it started up fine. Both cylinders seem to be working equally. It idles at around 1.7k but when i rev it, it doesn't return to idle. It also doesn't run without the choke on.

Air leak?


doesn't seem to be, I've checked the seal between the carbs and inlet mouths.
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Chris45
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PostPosted: 16:18 - 19 Nov 2017    Post subject: Reply with quote

Quote:
It instead would climb up and up past 6k.


Throttle valve/body problem if ever there was one. I'm still concerned about the air intake issue, reckon you should source/borrow an original air box and set everything up as original.

Otherwise double check the throttle valve again, sounds silly but have you fitted them in the right way round? Your quote sounds as if the valve is in upside down!

Four stroke machines don't have read valves, so we can discount that as a problemo.
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Jay2903
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PostPosted: 18:02 - 19 Nov 2017    Post subject: Reply with quote

Chris45 wrote:

Throttle valve/body problem if ever there was one. I'm still concerned about the air intake issue, reckon you should source/borrow an original air box and set everything up as original.

Otherwise double check the throttle valve again, sounds silly but have you fitted them in the right way round? Your quote sounds as if the valve is in upside down!

Four stroke machines don't have read valves, so we can discount that as a problemo.


If by throttle valve you mean carb slide yes they're fine, in the correct way. I don't think it would be possible to put these ones in the wrong way around. The bike seemed to run ok with the original airbox but it wouldn't be possible to fit it again.
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Jay2903
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PostPosted: 18:49 - 19 Nov 2017    Post subject: Reply with quote

i've messed about a bit and i think its got to be the mixture being off thats causing the problems.

I have it idling at 2k with the choke off. When i rev it returns to idle, maybe a bit slowly. I took it for a little ride round the block. seems about ok slow but when I open the throttle it splutters.
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Fizzer Thou
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PostPosted: 19:04 - 19 Nov 2017    Post subject: Reply with quote

You need to check the gaskets between the cylinder head and the inlet manifolds Thumbs Up

Part #1 on the fiche

https://www.cmsnl.com/yamaha-xs500-1977-1h3-europe-1h228-198e5_model37276/partslist/0025.html#results
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Chris45
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PostPosted: 19:25 - 19 Nov 2017    Post subject: Reply with quote

Quote:
but when I open the throttle it splutters.


Classic fuel starvation/too lean a mixture. Still convinced this is a simple air/fuel mixture problem, very likely eminating from the air box side. Wondering if you can have the carbs balanced? Also recheck for any splits/air leaks on the intake side. Are the intake rubbers securely clipped and/or tightened up properly? Sometimes a connection may look tight, but when the engine is running, air may be getting draw in between the carb and intake port.

Hate these little problems, they are so simple yet drive me demented Evil or Very Mad
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