Running Issue

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podman
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Running Issue

#1 Post by podman » Mon Apr 03, 2017 12:55 pm

Any help or advice appreciated with my 500 please.

It seems I have an intermittent running issue with my bike, sometimes it will run and rev out fine, pull as it should and have a great kick to it but Sunday just past, whilst still starting first kick and running well until 6k, pass that it feels flat, doesn't want to pull and has no kick to it.

Occasionally a burst of power will kick in, performance will resume as normal and then it will fade off again, 5 mins later,I may be luck to receive another burst of power.

I was initially thinking fueling but after the last ride out, im beginning to think its more electrical, its like another cylinder is chiming in or the power vales are open.

Over Winter the bike has had a carb refurb and set up(power vales, oil pump), I also replaced the fuel tap with a new Yam item just last week as it was leaking.

I was initially thinking of replacing the plug caps(originals are fitted) along with new plugs (they have maybe only done around 100 miles thou) in case one or more caps are past it.


I have fitted "R" plugs to the bike but I understand the OE caps are not for resistor plugs, wouldnt cause that much of a problem thou would it?

Any suggestions welcome.

Thanks.

begbie
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Re: Running Issue

#2 Post by begbie » Mon Apr 03, 2017 1:21 pm

The servo shares a circuit with the fan switch. I would be looking around this area.

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tacky1
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Re: Running Issue

#3 Post by tacky1 » Mon Apr 03, 2017 4:12 pm

Sounds like a bad cap or a fouled plug, Mine was doing something similar, Are you running stock jetting.
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
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podman
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Re: Running Issue

#4 Post by podman » Mon Apr 03, 2017 4:14 pm

Yes, everything is stock. Thanks.

silverstrom
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Re: Running Issue

#5 Post by silverstrom » Mon Apr 03, 2017 6:11 pm

Start with old parts that should have been replaced already. If your plug caps are original they definitely need to be replaced. New NGK resistor caps are cheap and will last another 20 years. Cut 5 mm from the plug wires before screwing the new caps in.

Do one thing at a time so you can be sure that you understand what solved the problem. If the new caps don't help then try new spark plugs. It is possible that one (or more) of your new spark plugs is defective. Make sure you are using resistor plug and resistor caps. Really you only need one of the other, but both is always best. If you have non-resistor plugs the electrical interference they cause can affect your CDI with results similar to what you are experiencing now.

Electrical faults will have similar effects to fuelling problems. It can be tricky to properly diagnose.

BigGuy
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Re: Running Issue

#6 Post by BigGuy » Mon Apr 03, 2017 8:14 pm

silverstrom wrote:Start with old parts that should have been replaced already. If your plug caps are original they definitely need to be replaced. New NGK resistor caps are cheap and will last another 20 years. Cut 5 mm from the plug wires before screwing the new caps in.

Do one thing at a time so you can be sure that you understand what solved the problem. If the new caps don't help then try new spark plugs. It is possible that one (or more) of your new spark plugs is defective. Make sure you are using resistor plug and resistor caps. Really you only need one of the other, but both is always best. If you have non-resistor plugs the electrical interference they cause can affect your CDI with results similar to what you are experiencing now.

Electrical faults will have similar effects to fuelling problems. It can be tricky to properly diagnose.
I agree, if it persists you could also check the coils for a good earth (ground)? A bad ground can cause some weird issues.
Shake "N" Bake!

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phildu31
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Re: Running Issue

#7 Post by phildu31 » Tue Apr 04, 2017 4:53 am

Hi.
Symptoms you tell say it could be the power valves occasionnally not opening and so an issue in command box.
Does your motor have one or two cylinders misfiring or is it the entire motor short of power ?
Begin with the easiest : plugs and caps.
And if no change try to swap ( if possible ) the ypvs command box.

podman
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Re: Running Issue

#8 Post by podman » Tue Apr 04, 2017 10:50 am

Thanks for all the pointers, I aim to do the caps and plugs in the coming days and will feed back after that.

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1601pete
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Re: Running Issue

#9 Post by 1601pete » Mon Aug 05, 2019 4:35 pm

Appreciate this was a while ago but did you ever get to the bottom of the problem of it not revving out past 6k? Be interested to know what it was, as a friend of mine has the same problem and we have tried everything to try and fix with no luck. TIA

Linx
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Re: Running Issue

#10 Post by Linx » Mon Aug 05, 2019 4:44 pm

I had a similar issue which turned out to be a dodgy HT lead. I found the rear right exhaust wasn't getting so hot as the others. Changed that HT lead and fixed. Then changed the other 3 too.
:smt006 Current Bikes
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podman
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Re: Running Issue

#11 Post by podman » Mon Aug 05, 2019 4:48 pm

1601pete wrote: Mon Aug 05, 2019 4:35 pm Appreciate this was a while ago but did you ever get to the bottom of the problem of it not revving out past 6k? Be interested to know what it was, as a friend of mine has the same problem and we have tried everything to try and fix with no luck. TIA
Yes mate, the crank seals where goosed and depending on the air temp and tempreature of the engine, the seals would either grip for a short period of time(and id get power) , as the bike warmed, they would slip/fail again and power would drop along with the reluctance to rev out.

The piston rings had also stuck into their grooves so power was well below what it should have been anyway...thats the problem with buying low mileage bikes and/or that have sat around unused for long periods of time...

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1601pete
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Re: Running Issue

#12 Post by 1601pete » Mon Aug 05, 2019 5:02 pm

Ok thanks. Out of interest what made you look for that? And how did you test for it?

Did it rev ok in neutral and not under load?

podman
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Re: Running Issue

#13 Post by podman » Mon Aug 05, 2019 6:41 pm

Yes, it was fine in neutral and not under load which made it all the more confusing.

In the end I put it on a dyno hoping to find what electrical item was breaking down but after a few runs power dropped from 65bhp to 50 and dyno man said straight away it was the crank seals.

Any 2 stroke doesn’t like to be sat around not being run, the 500 even more so it would appear.

If your friends bike has an unknown history or you believe it’s been sat a while, from my expierence and what I’ve read here, chances are the seals are shot but start with the simple things like plugs/leads etc first of course...let us know how you get on.

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phildu31
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Re: Running Issue

#14 Post by phildu31 » Mon Aug 05, 2019 6:46 pm

crank seals => pressure test

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1601pete
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Re: Running Issue

#15 Post by 1601pete » Mon Aug 05, 2019 6:52 pm

We’ve tried everything

Swapped out with known good...coils, CDI, Powervalve controller, plugs, leads.

Rebuilt carbs, checked floats height, changed needle heights etc

Checked compression, all good and even across all cylinders

Rewired loom....

The list is endless. It did have a top end rebuild at least 3 years ago and hasn’t really turned a wheel since. So it has been stood so crank seals could be a possibility.

How can I test to check without ripping the motor apart? Leak down pressure test?

TIA

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