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xs500 not starting (driving me crazy)

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Jay2903
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Joined: 03 May 2016
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PostPosted: 19:26 - 19 Nov 2017    Post subject: Reply with quote
Fizzer Thou wrote:
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


I think they're fine. I sprayed around there when checking for leaks and the revs didn't change. It also wasn't doing this when i had the original airbox on.
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Jay2903
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PostPosted: 19:39 - 19 Nov 2017    Post subject: Reply with quote
Chris45 wrote:
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


I'm fairly certain there aren't any leaks downstream of the carbs. On the other side theres a set of new pod filters.

This is getting confusing. I thought when the idle speed hangs up, the mixture is too rich. But the splutter when throttle open is fuel starvation ?
Would this mean in need a bigger main jet ?
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Bru
Trackday Trickster



Joined: 01 Feb 2007
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PostPosted: 20:16 - 19 Nov 2017    Post subject: Reply with quote
Any chance the throttle cable or slide is sticking? Happened to me, due to a mis-routing problem. Could be checked off by revving at full swing of the bars, both sides.

Clutching at straws now...
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Jay2903
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PostPosted: 21:00 - 19 Nov 2017    Post subject: Reply with quote
Bru wrote:
Any chance the throttle cable or slide is sticking? Happened to me, due to a mis-routing problem. Could be checked off by revving at full swing of the bars, both sides.

Clutching at straws now...


Nope, throttle cable moves freely. I've replaced the slides because they were sticking already.
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bypass2
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Joined: 12 Sep 2013
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PostPosted: 23:32 - 19 Nov 2017    Post subject: Reply with quote
maybe fuel stavation from the petrol tap. the throttle cable might be moveing freely but it still has to be routed the correct way.
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Jay2903
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PostPosted: 01:22 - 20 Nov 2017    Post subject: Reply with quote
bypass2 wrote:
maybe fuel stavation from the petrol tap. the throttle cable might be moveing freely but it still has to be routed the correct way.


Throttle cable is definitely routed correctly. It has a honda cb 250 tank with a new fuel tap.
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Suntan Sid
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Joined: 07 May 2009
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PostPosted: 11:55 - 20 Nov 2017    Post subject: Reply with quote
Jay2903 wrote:
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 ?


Are both pilot jets set to the correct turns out, as recommended by the manufacturer?
The pilots control zero to 1/4 throttle, if they're not set correctly you will have difficulty starting and achieving a smooth idle.
As I said before are you absolutely certain the diaphragms are seated correctly and are 100% leak free?

Have you checked and tested the condenser for the points?
IME, when working on minis, the first port of call for an ignition problem would be a new condenser, 9 times out of ten it would cure the problem!
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Jay2903
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PostPosted: 15:10 - 20 Nov 2017    Post subject: Reply with quote
Suntan Sid wrote:


Are both pilot jets set to the correct turns out, as recommended by the manufacturer?
The pilots control zero to 1/4 throttle, if they're not set correctly you will have difficulty starting and achieving a smooth idle.
As I said before are you absolutely certain the diaphragms are seated correctly and are 100% leak free?

Have you checked and tested the condenser for the points?
IME, when working on minis, the first port of call for an ignition problem would be a new condenser, 9 times out of ten it would cure the problem!


recommended pilot setting are 1 - 1 1/4 turns out. I've been messing with this to try and make it run best with the pods. currently at 1 1/2 turns out.

These carbs have a different type of diaphragm. you can't really seat it incorrectly. They've been replaced as the last ones were leaking. Condenser in also new.
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Jay2903
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PostPosted: 15:54 - 20 Nov 2017    Post subject: Reply with quote
I've noticed today. before i start it, the fuel lines are full of fuel but when its running you can see the fuel dripping through. not sure it the petcock isn't flowing eneough or it's a carb problem. (petcock is new)
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bypass2
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PostPosted: 21:04 - 20 Nov 2017    Post subject: Reply with quote
if it is a cb250 petrol tap would that have enough petrol flow fore the xs500 carbs. maybe the cb250 tap is restricting the xs500 carbs
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Jay2903
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PostPosted: 00:40 - 21 Nov 2017    Post subject: Reply with quote
bypass2 wrote:
if it is a cb250 petrol tap would that have enough petrol flow fore the xs500 carbs. maybe the cb250 tap is restricting the xs500 carbs


I was thinking that, but could it be really using fuel faster than the rate it flows out of the fuel tap ?
If that were so it would have a range of like 10 miles.
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Jay2903
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PostPosted: 18:54 - 24 Nov 2017    Post subject: Reply with quote
I fitted a new fuel tap with two outlets rather than one. It didn't make any difference to the problem. At full throttle it stutters a lot. Im gonna increase the main jet size, should i go up one or two sizes ?
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bypass2
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PostPosted: 01:32 - 25 Nov 2017    Post subject: Reply with quote
what about the float heights are they set right. guessing what about the battery is that fully charged
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