Author Topic: Hesitancy and running rough at 3500 rpm  (Read 765 times)

Offline Filmcamera

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Hesitancy and running rough at 3500 rpm
« on: August 18, 2019, 08:19:14 AM »
I got back yesterday from a two up 400 mile ride over two days that took a total of eight hours (trust that is good going for Costa Rica!).


All in all the bike ran well but there is a major hesitancy or reluctance to rev that starts at about 3500 rpm and goes on up to 4100 or so.  In that range the bike does not pull at all and feels like it is out of gas or is missing on one cylinder.  As soon as it gets past that range it pulls fine again. 


This happens in every gear but is more noticeable in 3rd, 4th and 5th.


I have no idea what is the cause so if anyone can point me in the right direction I would appreciate it.


The clutch also slips badly if I roll on hard in high gear but that is probably just oil on the clutch I think.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline daveson

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Re: Hesitancy and running rough at 3500 rpm
« Reply #1 on: August 18, 2019, 08:58:34 AM »
Hi

I have a memory a while ago your bike had unacepable compression on cylinder 1 and 2 and that you could hear air escape from 1 and 2 with a leak down test.  Also you had an overheating problem. This made me think you have a leaking gasket between 1 and 2.

I would think that's an urgent task.  If you havn't had the problem long,  it might be fixed just by tightening the head bolts if they're loose (or check for stretch)  The longer it's left the more likely the gasket is burnt and needs replacing

I know I shouldn't say this but many people,  including myself, have got years extra out of a failed gasket with the copper based additive.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #2 on: August 18, 2019, 04:24:37 PM »
Back in June you wrote, from cylinders 3 and 4 there is no audible leak that I can hear, cylinder 2 it seems to escape through cylinder 3 and cylinder 1 I am not sure, maybe the throttle bodies.

Top dead center on the compression stroke should be used for the leakdown test so then:
If cylinder 2 can be heard leaking into cylinders 1 and 3, that's a head gasket problem which will also have effects on the performance of cylinder 1 and 3; if cylinder 2 can also be heard leaking through its throttle body, that's an intake valve problem.

It might be time now to repeat both tests to determine if there have been changes.  Is your moto's fan running more than it usually does this season?
At least you have the Street Triple to keep you sharp.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
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Offline johnny

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Re: Hesitancy and running rough at 3500 rpm
« Reply #3 on: August 18, 2019, 04:45:08 PM »
greetings...

sounds like sticky injectors...

wanna getts liquid low friction isertopes of molybendernum for petrolium gasolines in the tank...


* Backup_200603_lub101-crystal-structure.gif (22.9 kB . 250x519 - viewed 104 times)

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #4 on: August 18, 2019, 05:10:09 PM »
wanna getts liquid low friction isertopes of molybendernum
Use this map to getts there.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #5 on: August 19, 2019, 07:54:15 AM »
Thanks for the replies. I am planning to redo the compression and leak down tests today, I will also tighten the head bolts.  I looked in Clymer and found out how to determine TDC on cylinder #1 but how to I then know that I am on the compression stroke not the exhaust stroke for the other 3 cylinders? Does it simply go in order of the firing order so after the compression stroke for 1 if I turn the engine it would be 3 then 4 then 2? 
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline daveson

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Re: Hesitancy and running rough at 3500 rpm
« Reply #6 on: August 19, 2019, 08:08:58 AM »
Yes. Anticlockwise. And you will also see the valves are closed (cam lobes facing up)

Set your torque wrench to the final setting 36 ft. -lb. If any bolts turn at that setting, they're loose (also it takes more to start the turn,  than to achieve it)

You can also find if it's the compression stroke without removing the cam cover with a finger over the plug hole,  although difficult on a brick you might extend it with a hose type thing.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #7 on: August 19, 2019, 02:47:35 PM »
Don't take shortcuts. Remove the camshaft cover so you can verify clearly what's happening.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #8 on: August 19, 2019, 03:04:43 PM »
I will, though having just done the compression test I am already seeing some troubles.  Last time I did a compression test I got a consistent 120-125 psi in all four cylinders.  Today I got


Cylinder 1 - 125
Cylinder 2 - 130
Cylinder 3 - 120
Cylinder 4 - 90


That is not good at all  :yawl:


I am waiting for the engine to cool and I will check the valve clearances again then do the leak down test.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #9 on: August 19, 2019, 03:47:27 PM »
Looking at my Clymers it seems to indicate that to remove the timing chain cover I have to drain the oil, remove the crankcase cover, remove the Hall sensor cover and hall sensor itself and also remove the oil pressure sensor. Then I an finally remove the timing chain cover. Is that right?
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline daveson

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Re: Hesitancy and running rough at 3500 rpm
« Reply #10 on: August 19, 2019, 04:55:19 PM »
Was throttle wide open on 4 or something else wrong?

You don't have to remove the timing cover.

Consider removing the camshaft cover in the morning so you can be confident the engine is cold and readings good.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #11 on: August 19, 2019, 05:05:11 PM »
Looking at my Clymers it seems to indicate . . .
You don't need to do all that to check the valve clearances or do a leakdown test. Supply the chapter and pages to which you are referring.

Isn't doing those tasks your current goal? If the engine hasn't been run, you're ready to move ahead.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #12 on: August 19, 2019, 06:45:10 PM »
Page 93 of Clymers seems to say I need to have the timing chain cover off to find TDC but I guess I can do it another way.  I was also thinking though that since I am this far in I might as well remove the cams to get to the buckets and measure them so I can order new ones and finally get the valves in spec.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline daveson

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Re: Hesitancy and running rough at 3500 rpm
« Reply #13 on: August 19, 2019, 08:23:01 PM »
Leave the cams in,  measure the clearances with a feeler gauge.

With the spark plug removed,  you will see the piston approaching TDC.  When you see the valves are closed on cylinder one they will be open on cylinder four, then you will know cylinder one is on the compression stroke.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #14 on: August 19, 2019, 08:27:51 PM »
I have done the clearances before. There are a few valves out of spec - too tight.  In order to fix that I need to take out the existing buckets and see what size they are so I can order the correct size replacements to put the valves back into spec.  That is a pain but needs to be done and since it is not looking good for cylinder four now is the time to do it, I do not think I will be riding the bike again until the engine is back in shape.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #15 on: August 19, 2019, 08:43:23 PM »
Page 93 discusses camshaft removal. I was under the impression you were doing a leakdown test—a project for which instructions for finding top dead center of a piston in its compression stroke have been explained previously.

Are you doing the leakdown test or are you going straight to camshaft disassembly for bucket replacement? That procedure follows a different course. What are your clearance numbers?
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #16 on: August 19, 2019, 08:52:45 PM »
I am doing a leak down test and also rechecking my valve clearances - the last time I checked them I had two intakes at 0.13 and two at 0.15 with two at 0.18 and two at 0.20 so I have two under min two at min and four within spec.  All exhaust valves are within spec.


My plan was to recheck the valve clearances (especially after today's cylinder 4 compression test) then do the leak down then take off the camshafts so I can see what buckets I have in there now and order new ones to bring all intake valves to the upper limit of spec (0.20mm)


Also depending on the results of the leak down test I might need to be ordering a head gasket, oil rings or all manner of things - time will tell.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline Scott_

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Re: Hesitancy and running rough at 3500 rpm
« Reply #17 on: August 19, 2019, 10:09:53 PM »
filmcamera, not to make an assumption, but--- you are going to measure ALL of your buckets and make a listing for your future reference?? not just the tight ones.
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Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #18 on: August 19, 2019, 10:19:05 PM »
I will measure all of the intake buckets for sure.  If, when I check the clearances of the exhaust valves tomorrow, they are all still in spec, I might skip measuring those buckets just so I do not have to remove the exhaust cam as well.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline daveson

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Re: Hesitancy and running rough at 3500 rpm
« Reply #19 on: August 19, 2019, 10:39:43 PM »
 The leak down test will tell you more.

A leaking head gasket can sometimes be fixed without removing the head,  depending on the cause.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #20 on: August 20, 2019, 01:31:59 AM »
two intakes at 0.13 and two at 0.15 with two at 0.18 and two at 0.20I have two under min two at min and four within spec.  All exhaust valves are within spec. . . .  order new ones to bring all intake valves to the upper limit of spec (0.20mm)
What you have are six intake valves at spec. Valve clearances are out of spec when they are below or above specification. You can bring the two at 0.13mm up to 0.18mm. The two at 0.15mm are at spec. Buckets sell for around 35USD each. Unless the buckets from the 0.13mm valves clearances can be used, it will take at least $70 for buckets to reset valves that are at spec already and make them valves that are still at spec. There's nothing needed to be done with the two at 0.18mm because they are at spec; furthermore, buckets are sized at 0.05mm increments so you couldn't set them at 0.20 even if it were beneficial to do that.
My plan was to recheck the valve clearances (especially after today's cylinder 4 compression test) then do the leak down. . . . Also depending on the results of the leak down test I might need to be ordering a head gasket, oil rings or all manner of things.
That's a good plan. You won't know what to order until you remove the cylinder head. Squirting oil into the cylinders then repeating the compression test reveals ring problems if the numbers rise significantly.

You'll need to listen carefully during the leakdown. If a head gasket were leaking between two cylinders I'd expect to see significantly lower compression values than in their previous tests, and an engine running hotter than usual.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #21 on: August 21, 2019, 02:15:42 PM »
I rechecked the valve clearances today and redid the leak down test making sure I was at TDC for each cylinder first.


The valves were basically the same





The leak down test was VERY differenet to the first time I did it so I guess I was not at TDC before.


Cyclinder 1





Cylinder 2





Cylinder 3





Cylinder 4





As you can see cylinder is 4 is no worse than the others.  My next step is going to be to put everything back together again and redo the compression test on cylinder 4.


Listening for leaks the only place I could really hear any hiss seemed to bo coming out of the timing chain area (I did the tests with the cam cover OFF so I could see where the lobes were to verify TDC for each cylinder)


It is time to sort out the valves though so after that I will take out the buckets to measure them and order new ones.  I plan to make sure the YES size is 0.20mm across the board for the intake valves if possible.


The exhaust ones I will measure but do not plan to replace any at this point.







  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #22 on: August 21, 2019, 04:40:21 PM »
I plan to make sure the YES size is 0.20mm across the board for the intake valves if possible.

The best laid schemes
o' mice an' men
Gang aft agley  from To A Mouse by Robert Burns
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Filmcamera

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Re: Hesitancy and running rough at 3500 rpm
« Reply #23 on: August 21, 2019, 04:43:27 PM »
That they do - hence the "if possible"  :bmwsmile
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
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Offline Laitch

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Re: Hesitancy and running rough at 3500 rpm
« Reply #24 on: August 21, 2019, 04:46:49 PM »
That they do - hence the "if possible"  :bmwsmile
It isn't possible.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

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