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  #1  
Old 30 Oct 2009
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R80GS Tuning probs
Just fitted new header pipes and new push rod tubes. Started up the bike and the bike sounded ok at idle but a blip of the throttle caused a slight mis-fire at higher revs. I noticed the right hand down-pipe was getting glowing red hot compared to the left which remained ok. The neutral light when at idle was ok but when i hit the revs it seemed to glow noticably brighter although the charging light itself went out as normal.
I ran out of daylight before I could balance the carbs so this will make some difference but the glowing header did concern me. Appreciate any words of wisdom before facing it again tomorrow. Cheers
Mark
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  #2  
Old 30 Oct 2009
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Sounds to me like you have set the valves wrong to the timing - did you put everything back in the correct order and place it where it came from - pushrods back where they came from eg left exhaust to left exhaust etc if you have mixed things up it may cause problems, maybe the push rod have not been seated correctly or the barrel, heads or cams have not seated correctly when torqued down I would suggest you remove everything and re check your work and each component make sure you have not bent a pushrod or put anything back on in the wrong place. Then turn the engine over by hand slowly and watch that the whole sequence of tdc and valves opening closing is correct. This is not going to be a carb problem if you have not touched them - the flame front is burning in your exhaust making it glow. Did you check the condition of your valves and seats before re assembly.
Was the bike fine before you did the work ? have you altered anything else.
If not it seems simply that the exhaust valve is opening too soon or not closing properly for some reason.
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Old 30 Oct 2009
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I double checked everything before i put it back. I cleaned all valves and seats and piston and reset valves accordingly. The battery is dead, I was using a jump start to fire up which may allow for erratic misfire but i am not sure about the burning in the header pipe
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Old 30 Oct 2009
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Amazing!

I've tried to get my down-pipes to turn orange, but have faild to even with 1000cc system.
Let me know how you manage to do it!

What you have is way too hot exhaust fumes...
* timing off
* valveplay off
* jetting off
* air leakage (leaning the mixture to way off)
* jammed choke return
* spark problems
* changed back-pressure from exhaust system (ex., dual to single or vice versa)
* changed airfilter from stock paper to K&N or similar

Is your version equipped with the exhaust return system crap ? Those were said to cause weird phenomenas and overheating problems...
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Old 30 Oct 2009
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Hi
The main difference is that I changed from a fron balnce pipe set up to no balance pipe into a y-piece. I will balance the carbs tomorrow and re-check the valve clearences and see if it makes a difference
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Old 31 Oct 2009
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Quote:
Originally Posted by simplemind View Post
Hi
The main difference is that I changed from a fron balnce pipe set up to no balance pipe into a y-piece.
That's not good...
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Old 31 Oct 2009
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Alibaba what would you suggest as a rough basic idea of rejetting to when doing as Simplemind have done by chaning the back-pressure so radically as he have done?

Whould a lift of the needle (one or two notches) and a change to next larger main-jet be fairly ok guess work, or would you recommend as I would => workshop with proper tools to adjust the mixture correctly?

I've tested s/s "megaphone" (made in Australia sold by www.midland.se in Sweden) once on my R80. Loved the sound! But... lost all low rev torque => opted to stick with "stock" mufflers/silencers instead (have regretted that choice ever since -ROWL). My reason was that I was very concerned about what the effect would have on the exhaust fume temps, and rejettings were beyond my scope of knowledge back then.
Sounds very much like what Simplemind have done with his beemer , i.e. altering back-pressure way too much without rejetting the carbs accordingly...

Most interested to hear about your thoughts in/on the jetting theories/practicalities -
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