A properly hot engine does not want to idle

szabgab
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Posts: 115

A properly hot engine does not want to idle Sept 29, 2016 13:53:36 GMT

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Post by szabgab on Sept 29, 2016 13:53:36 GMT

Hi everybody,

I have a 400n that serves me extremely well. I did have some minuscule problems with it, but most of the time I was able to repair, whatever was needed on my own.

One thing I've found baffling is the tendency of the bike to 'lose' idle when very hot (like after a long stint of 30-40 miles on the road in the summer). It does idle, if you crank up the idle speed, so it looks like the basic 1200 or so RPM's drop to a steady 5-600. I did clean the carbs twice (due to some other issues), changed the plugs, cleaned the tank and so on. Is this something electric? The bike works just fine for shorter rides even in town in the summer in Hungary (where it often gets to 30-40 Centigrade), but once I leave town behind and ride the bike for a longer journey, the exact same thing happens.

Any ideas?

Thank you,

G

szabgab Full Member Posts: 115	A properly hot engine does not want to idle Oct 1, 2016 7:25:13 GMT via mobile PM Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by szabgab on Oct 1, 2016 7:25:13 GMT No ideas?

stevegbr Administrator ADMIN BIRMINGHAM Posts: 10,409 mini-profile background: {"image":"","color":"2b86e7"}	A properly hot engine does not want to idle Oct 1, 2016 10:10:51 GMT PM Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by stevegbr on Oct 1, 2016 10:10:51 GMT to be honest it could be a lot of things, first thing fuel, what are you using?
	bikes i have owned cb250na cb250n cb250rsa cx500 yamaha fs1e

mikef
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A properly hot engine does not want to idle Oct 1, 2016 10:24:20 GMT

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Post by mikef on Oct 1, 2016 10:24:20 GMT

Hi.
I know what you mean, I had a similar problem. I think the fault on mine was due to the inlet manifold rubbers.
Mine looked ok but when I pulled hard at the rubber it just came away from the aluminium body. In addition the rubber "O" rings were also flattened and were probably doing nothing.
I said previously "I think the fault ....", unfortunately at the same time I adjusted the mixture and balanced the carbs, so it could have been one of those things as well. So I would think a small air leak anywhere in the inlet side to give the symptoms that you have, maybe those little ribber "O" rings in the idle mixture adjusters.
Hope that helps.
Mike.

MikeF

ian Member Of The Year 2019 Isle of Man Posts: 5,400 mini-profile background: {"image":"","color":"29908d"}	A properly hot engine does not want to idle Oct 1, 2016 20:27:55 GMT srx600 likes this PM Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by ian on Oct 1, 2016 20:27:55 GMT I've never tried it myself, but I've read on the forum that sqirting wd40 or carb cleaner on the rubbers will show a leak as the revs will alter - worth a try?

szabgab
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Posts: 115

A properly hot engine does not want to idle Oct 1, 2016 22:32:12 GMT

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Post by szabgab on Oct 1, 2016 22:32:12 GMT

Hi guys, thanks for your answers.

Steve - I'm using what's available, ordinary 95 unleaded without any additives. The fuel system is clean - The tank has been de-rusted, filters cleaned, tap overhauled, engine line inspected, carb cleaned and balanced, in adition to the valve clearances. The bike runs a lot smoother since, but this thing persists.

Mike - I will have to try those things, although I pulled the carb apart and cleaned everything, I did not change a single rubber. The air valve cutoff membranes are just about OK (no holes in them as yet, but I'm getting close to that), all the o rings gone flat (I turned them around). The inlet manifold is OK, although somewhat lost it's flexibility and it is coming off the aluminium part. So I guess any of these points could cause the mixture to get too lean when metal parts are too hot?

Ian: I'll try your method. Makes sense, WD40 closes to pores and micro-holes on an ancient piece of rubber...

" You Meet The Nicest People On A Honda "

Post by szabgab on Sept 29, 2016 13:53:36 GMT

Post by szabgab on Oct 1, 2016 7:25:13 GMT

Post by stevegbr on Oct 1, 2016 10:10:51 GMT

Post by mikef on Oct 1, 2016 10:24:20 GMT

Post by ian on Oct 1, 2016 20:27:55 GMT

Post by szabgab on Oct 1, 2016 22:32:12 GMT