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Offline SnowOwl

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Loss of top end power
« on: October 12, 2017, 01:08:53 PM »
My 2016 bike is now at 4500 miles and for the past 500 or so I have noticed a serious lack of power on the interstate.  Yesterday I tried to pass a semi truck that was doing 60mph and my bike only managed to top out at 71mph  :232:.   I have also felt it has not been accelerating like it used to and overall is not performing.  I know this problem has been brought up before in this thread:

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But I wanted to start a new thread to bring it to the attention of any newcomers who may not have seen that thread.  In summary, this issue is likely the result of the valves tightening up.  So last night when I got home I tore the bike down to get at the valve shims.  Since it has to be at room temperature to get accurate measurements I let it sit over night, but preliminary checks show all the valves are tight, especially the far right intake and exhaust next to the cam chain.  In a little bit I will go measure them cold and see if they are still out of spec.  More to follow later today!
1982 Suzuki PE175
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Offline EscCtrl

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Re: Loss of top end power
« Reply #1 on: October 12, 2017, 02:51:33 PM »
That is exactly the way my bike was acting. I did a valve adjustment and replaced my spark plugs and all is well in the world. I have a post about doing a valve adjustment at 9000 miles. It started acting up around 7500 miles if I remember correctly.
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Offline SnowOwl

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Re: Loss of top end power
« Reply #2 on: October 12, 2017, 03:35:04 PM »
EscCtrl, your post is the one that lead me to the correct solution to this problem!  Thanks!

Here are my measurements:

Intake should be .16mm +- .03, so from .19 to .13:

.110, .127, .110, .110

Exhaust should be .27mm +- .03, so from .30 to .24:

.215, .215, .215, .190

So, they are all tight with one exhaust really tight!

Off to the local BMW dealer to buy shims.  We only have a BMW and a Harley dealer local here and Im not going to the Harley dealer!
1982 Suzuki PE175
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Online HerrDeacon

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Re: Loss of top end power
« Reply #3 on: October 12, 2017, 04:30:09 PM »
Wow, really surprising how early some bikes lose the clearance. I guess they must have left the factory closer to the tight end of the spectrum. Let us know how you make out with it and how it feels after.

I'm not really close yet to the suggested interval yet and could probably get away with waiting until next winter (I'm at 17,000 kms) but I'm going to check this this winter anyway just to see.
'14 CB500X / '82 MB5 / '78 XL250S / '72 CB350
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Offline SnowOwl

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Re: Loss of top end power
« Reply #4 on: October 12, 2017, 05:40:56 PM »
I have a friend with a 2013 model.  He has always been able to pull away from me.  I had assumed it was because I am heavier than him and I have a top box on.  Now I wonder if it came from the factory at the low end of the range and maybe a little out of spec.
1982 Suzuki PE175
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Offline EscCtrl

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Re: Loss of top end power
« Reply #5 on: October 12, 2017, 09:35:23 PM »
*Originally Posted by SnowOwl >>>> link hidden <<<<
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EscCtrl, your post is the one that lead me to the correct solution to this problem!  Thanks!

Here are my measurements:

Intake should be .16mm +- .03, so from .19 to .13:

.110, .127, .110, .110

Exhaust should be .27mm +- .03, so from .30 to .24:

.215, .215, .215, .190

So, they are all tight with one exhaust really tight!

Off to the local BMW dealer to buy shims.  We only have a BMW and a Harley dealer local here and Im not going to the Harley dealer!

You're welcome. I am happy it helped.


With a lot of other bikes, I have or have owned, after the first or second valve adjustment they seem to stabilize and need less frequent corrections. It's always good to keep a check on them. If you keep records, you can judge how long you can safely go before needing to check them the next time.

I ordered my shims from Honda parts direct in Texas. If I'm not mistaken, they are a supplier to dealerships.
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Artist also known as ben2go.
Six=Suzuki GS500,'00 V Star Classic,'14 CB500X farkled out nicely.
I rescue neglected and battered motorcycles.

Offline SnowOwl

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Re: Loss of top end power
« Reply #6 on: October 12, 2017, 11:44:04 PM »
I was able to find shims locally.  The sizes available let me adjust the intakes to right around .15mm and the exhausts to around .28mm.  Got it all back together about an hour ago and took it for a spin.  My impression of how it runs now is OMG!  :005:  Its a totally different bike!  There is a growl to the exhaust when blipping and on heavy acceleration over 5K RPM that was never there before.  There is far more power in the mid range and top end.  I had to watch it in 2nd and 3rd gear because I would quickly red line it, that never happened before.  It was always a chore to get it up to 8K RPM let alone red line.  I really believe it wasnt right from the factory, its so much better now.  I kept having to slow back down to the speed limit, spent way too much time over it.
1982 Suzuki PE175
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Online HerrDeacon

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Re: Loss of top end power
« Reply #7 on: October 13, 2017, 12:10:55 AM »
*Originally Posted by SnowOwl >>>> link hidden <<<<
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I really believe it wasnt right from the factory, its so much better now.

It certainly sounds like it. Really glad its made such a noticeable improvement.
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Offline jsonder

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Re: Loss of top end power
« Reply #8 on: October 13, 2017, 01:30:09 AM »
 :047:

I'm glad that you caught it before tolerances got even tighter.  For every "they never needed adjusting" story, there seems to be a "boy did they go out of spec fast" story.  When in doubt, inspect the clearance.  It isn't rocket science, but it is fairly time consuming and fiddly to do it right.

As you didn't mention spark plugs, I'm assuming that you left the old ones in.  Change them the next time you check the valves.

John  '14CB500XA (Daily Rider),  '09CRF230L (L'il Red Piglet), '89NX250 (sold)
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Offline SnowOwl

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Re: Loss of top end power
« Reply #9 on: October 13, 2017, 03:41:56 PM »
I didnt change the plugs.  I did pull and inspect, clean and gap them.  They arent due for replacement until 16K miles and they look good so I put them back in there.

Between purchasing a better feeler gauge set and 8 shims I only spent about $35 on this.  So glad I can do it myself and not pay a dealer $$$ to do it.  By doing it myself the bike was down less than 24 hours, a dealer would never be able to turn it around that fast.  Down time included overnight and time spent running around to get shims, actual working time for this job was about maybe 7 hours.  I took it slow, next time will be faster.
1982 Suzuki PE175
2016 Honda CB500XA

 


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