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Yamaha 250SR tickover problem

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flactem
L Plate Warrior



Joined: 28 Nov 2021
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PostPosted: 19:46 - 28 Nov 2021    Post subject: Yamaha 250SR tickover problem Reply with quote

1982 model with 24,000 miles from new on the engine. Excellent condition and everything works, but there is a tickover problem when stationary. Tickover is set at 1k revs and will hold for a few seconds (3 or 4), but the revs can then unexpectedly rise to 3k even though the throttle is closed. This action is erratic and the tickover can sometimes be held at around 1k revs by manipulating the throttle. (Occasionally the tickover revs rise even higher at which point the engine is then killed.) The throttle control when riding is otherwise normal. The carbs were fully examined including checking diaphragms for pinholes. Any advice or suggestions would be most welcome. Flactem.
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yen_powell
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PostPosted: 19:52 - 28 Nov 2021    Post subject: Reply with quote

When I have had this on an XL250R in the past it was the rubber between the engine and the carb sucking in air even though it looked fine, a new one fixed my problem.
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Nobby the Bastard
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PostPosted: 20:41 - 28 Nov 2021    Post subject: Reply with quote

yen_powell wrote:
When I have had this on an XL250R in the past it was the rubber between the engine and the carb sucking in air even though it looked fine, a new one fixed my problem.


This.
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stinkwheel
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PostPosted: 21:10 - 28 Nov 2021    Post subject: Reply with quote

As above, most likely an air leak. The usual test is to get it idling then spray WD40 or carb cleaner or similar over the inlet rubber, if it revs up, that confirms the leak. Careful not to set yourself on fire when doing this test.
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Easy-X
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PostPosted: 12:25 - 29 Nov 2021    Post subject: Reply with quote

This a 2-stroke? There's also the crank seals but they tend to suck in air when the engine's under load.
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A100man
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PostPosted: 13:07 - 29 Nov 2021    Post subject: Reply with quote

Easy-X wrote:
This a 2-stroke?


No.
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jaffa90
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PostPosted: 18:49 - 29 Nov 2021    Post subject: Reply with quote

If not the above statements does the fuel tap have 3 positions or if not does the vacuum pipe smell or contain fuel?
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Pete.
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PostPosted: 19:28 - 29 Nov 2021    Post subject: Reply with quote

stinkwheel wrote:
As above, most likely an air leak. The usual test is to get it idling then spray WD40 or carb cleaner or similar over the inlet rubber, if it revs up, that confirms the leak. Careful not to set yourself on fire when doing this test.


A propane torch (unlit) does the same job with much less mess and risk.
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flactem
L Plate Warrior



Joined: 28 Nov 2021
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PostPosted: 22:01 - 30 Nov 2021    Post subject: Reply with quote

A similar problem with tickover (post subject "bike revs up") was resolved by skikman on 6June 2012 by adjusting the timing by one cog. But I think this was the SR 250 single, which of course has a completely different timing set up to the SR 250 twin.
However, I would like to check out the timing on my twin but lack the information. Any advice or help with info on timing marks location and method of adjustment of the chain for the SR 250 twin would be much appreciated.
Many thanks, Flactem.
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A100man
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PostPosted: 22:13 - 30 Nov 2021    Post subject: Reply with quote

A Twin you say?! One of these..??

https://global.yamaha-motor.com/showroom/cp/collection/srv250/

Never heard of that before, an import I'm guessing. I'm going with the air leak theory myself and easy to test as has been suggested. I'd go with the gas torc too if you have one.
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flactem
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PostPosted: 11:22 - 01 Dec 2021    Post subject: Reply with quote

SR250 Special is a parallel twin made by Yamaha 1980 to 1983 in USA and Spain. Flactem.
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jaffa90
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PostPosted: 01:32 - 10 Dec 2021    Post subject: Reply with quote

Thank you for your reply!!!!!!!!!!!!!!
flacteM or Metcalf???????????
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Old Thread Alert!

The last post was made 2 years, 110 days ago. Instead of replying here, would creating a new thread be more useful?
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