August 24th, 2022, 04:44 PM | #1 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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Bad vibes
I have caught the ninjette bug and picked up a 2nd ninja 250R. Its a race prepped 2010 with a "fresh" motor with one race day on it. When I got it it ran real nice and smooth.
Took it to The Ridge in WA. Down shifted too far going into the carousel and spun it up real hard. At that moment it started to have a vibration. Not super terrible but enough to numb my hands after a while. It is present all the time, in whatever gear, stationary or not- but is strongest under load on the gas low in the rev range. My guess is that I threw off the timing somehow, but really have no idea. Any thoughts on where to start or similar experience is appreciated. Thanks much. |
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August 24th, 2022, 06:16 PM | #2 |
ninjette.org certified postwhore
Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot.
MOTY - 2018, MOTM - Nov '17
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Do compression test...
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August 24th, 2022, 06:59 PM | #3 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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October 10th, 2022, 06:35 PM | #4 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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October 10th, 2022, 10:50 PM | #5 |
ninjette.org certified postwhore
Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot.
MOTY - 2018, MOTM - Nov '17
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Those compression results doesn't explain vibration levels.
Yes, do valve-clearance measurements... |
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October 11th, 2022, 07:43 AM | #6 | |
Guy Who Enjoys Riding
Name: Jim
Location: North Carolina
Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot.
MOTM - Oct '18, Aug '17, Aug '16
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Quote:
I'm trying to think of what could have disrupted the engine balance when it was over-revved. Is everything OK under the alternator cover? Last futzed with by Triple Jim; October 11th, 2022 at 10:12 AM. |
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October 11th, 2022, 04:04 PM | #7 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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What do you mean by ok? Is there something specific I should look for? Could timing being off throw off only one cylinder? Seems unlikely......
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October 11th, 2022, 05:05 PM | #8 | |
Guy Who Enjoys Riding
Name: Jim
Location: North Carolina
Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot.
MOTM - Oct '18, Aug '17, Aug '16
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Quote:
I don't know why the timing would have changed due to an overrev, and I don't know why valve adjustment would change either, but who knows at this point? Now if a chunk of a piston skirt came off, that would cause an imbalance. I guess it would take removing the oil pan to check for that unless there were a way to get a small video camera (borescope) in the crankcase somehow. |
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October 11th, 2022, 07:05 PM | #9 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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That all makes sense. Im going to start with valves since that requires removing a ton of stuff anyway and then give everything a look see once its open. It's a "fresh" motor. People who have raced against it (previous owner raced it) say "that bike has a good motor" so hopefully it's something easy to spot. I would just do the top end but I don't want to lose the "good motor" magic unless I have to.
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October 20th, 2022, 07:44 PM | #10 | |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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Quote:
Water pump also looks good. Putting it back together and will check vibration levels. Going to check motor mount torques, etc as I do this. |
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October 24th, 2022, 09:29 PM | #11 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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So compression is the same (-5psi) with the valves adjusted. #1 205psi #2 180psi. Could this compression imbalance cause the vibrations? Could the imbalance be related to carb sync somehow?
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October 25th, 2022, 12:07 AM | #12 |
ninjette.org certified postwhore
Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot.
MOTY - 2018, MOTM - Nov '17
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nah, those compression numbers are good. Difference is around 10% and won't cause you that dramatic of vibration.
This point, I'd get USB borescope and take look in cylinders from spark-plug hole. Can also look at bottom of pistons with sidecases off. |
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October 25th, 2022, 04:15 PM | #13 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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OK. Am I looking for broken bits or something else? And, what is the maximum out of balance in the compression department? Thanks.
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December 6th, 2022, 06:21 PM | #14 |
Retired motorcycle Mc.
Name: Robert
Location: Weed, California.
Join Date: Jul 2021 Motorcycle(s): 2012 Kawasaki Ninja 250R, 2021 CSC TT250, 1977 Triumph Bonneville 750cc,2001 Honda XR650L. Posts: A lot.
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Could that dramatic downshift and overrev have caused a key way to sheer ? is there a key on the altenator ? even almost sheering a key can go unknoticed sometimes
.... at first I thought a skirt of a piston parted and is now in the oil sump causing the imbalance but now I'm not so sure. I am assuming the vibration changes it's tempo with the RPM right ? (clutch in or out) meaning it is directly related to the crank some how, main shaft in the transmition holds the clutch basket and one of the pieces of the basket could have separated. but sense he had the covers off and no visible damage that's out.... that would be easy to see. .... so my guess is the lower compression piston did a no-no perhaps a skirt half is missing but the rings are still holding fairly good compression... that would be very odd but it has happened before. .... the bore scope is an great idea ! through the spark plug holes and up the filter cavity should show the culprit !.... .... Danno is the crank pressed together or a one piece cut crank ? if it's pressed together it's possible that the crank has slipped and twisted ! ( I had a xs650 yamaha that did that)...and it vibrated and rumbled alot.... it ran great but the rumble was from the crank gear moving closer and further away from the clutch basket (bent crank) and yes it sped up and slowed down with the RPM ...... I'm betting on a piston skirt regardless ! .... Bob......
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Its too late when you've gone too far ! |
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December 18th, 2022, 11:40 PM | #15 |
ninjette.org member
Name: Mike
Location: Dillsburg, PA
Join Date: Oct 2021 Motorcycle(s): 08' ninja 250 and Honda XL600 Posts: 31
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You won't find your answer here, you need to just dig in deep. Might never find it because it might just be a bent part, like a bent connecting rod or crank. At that point you've replaced the engine or are already rebuilding, as measurements can't really be taken with the part installed
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December 21st, 2022, 08:16 PM | #16 |
ninjette.org member
Name: Ben
Location: Portland
Join Date: May 2022 Motorcycle(s): '10 Ninja 250R (track), '20 Street Triple 765 (street), '12 CRF150R SM (racing) Posts: 55
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Chased down as much as I could without taking the engine apart. No clue. My racer buddy rode it and says just ride it. I'm going to just ride it. Maybe it will blow up bad enough I'll have to dig all the way in. Thanks for the help.
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