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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: technostructural on May 24, 2015, 09:56:38 PM

Title: 89 K75 Runs Rough Only when Hot - Troubleshoot
Post by: technostructural on May 24, 2015, 09:56:38 PM

Hello motorbrickers,

My 89 K75 runs absolutely beautifully upon startup, but as it gets warmer, it starts to run rougher. When nearly at full temperature, it will stutter when I give it a shot of gas. From my limited experience, this sounds like tight valve clearances: when the engine heats up, the valves expand and are not leaving enough clearance.

I thought I would check the clearances (as I have not done this since owning the bike) in any event, but I am curious to know if any of you have thoughts as to what else might cause this issue? Supposing the valve clearances are all perfect, where would be the second place I look?

Thanks.

Title: Re: 89 K75 Runs Rough Only when Hot - Troubleshoot
Post by: Scott_ on May 24, 2015, 11:28:32 PM

Water temp sensor would be my next suggestion after you check the valves, then possibly the HES sensors on the front of the engine.
Air temp and air flow also affect the fuel mixture, but I don't think issues with them would appear as it warms. I'd think that issues with them would be at cold and warm both.