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Engine locking then unlocking, then locking...etc...

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jeffyjeff
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PostPosted: 15:38 - 06 Mar 2021    Post subject: Reply with quote

it will be very interesting to see if this condition remains after the top end is removed. Sure sounds like a hydrostatic lock of some sort, but what? I believe you have removed that possiblity on the top end already. If the condition persists after removing the piston and cylinder, maybe related to the oil pump and lube system..obstruction? pressure relief valve sticking? Thinking Maybe see if the problem remains with the oil drained out of the engine.
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steve the grease
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PostPosted: 17:18 - 06 Mar 2021    Post subject: Reply with quote

Hmmmm, I'm beginning to change my original conclusion and lean more towards the roller/ball race jamming idea , rather than the stuck bore idea. the engine will have to be stripped further to find out for sure though.
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virus
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PostPosted: 20:41 - 06 Mar 2021    Post subject: Reply with quote

steve the grease wrote:
Hmmmm, I'm beginning to change my original conclusion and lean more towards the roller/ball race jamming idea , rather than the stuck bore idea. the engine will have to be stripped further to find out for sure though.


IF its one of the oilcooled gsxr750 engines then I doubt it would be a bearing, they have shell bearing crank journals. The first roller bearing in the assembly is the clutch/gearbox input shaft but he's said it happens with the clutch basket fitted or not.
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jeffyjeff
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PostPosted: 02:53 - 07 Mar 2021    Post subject: Reply with quote

virus wrote:
IF its one of the oilcooled gsxr750 engines then I doubt it would be a bearing, they have shell bearing crank journals. The first roller bearing in the assembly is the clutch/gearbox input shaft but he's said it happens with the clutch basket fitted or not.

Wonder if one of the main caps got installed backwards, or swapped from its original location? Still, seems if that were the case, the high rotational friction would manifest all the time. Does this engine have a plain bearing or washer to take up end thrust? I've seen engines bind up when the thrust bearing is mis located.
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Pete.
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PostPosted: 07:59 - 07 Mar 2021    Post subject: Reply with quote

MG#43 wrote:
Polarbear wrote:
So all you are turning is the crank and pistons? Everything else is disconnected?


thanks for reply.

correct.

When i put the bike back together (did some bottom end work), the bike just clicked once at the point of starting. With everything else checked, it turned out that the engine would not turn over, so I soaked in wd and rotated from the magneto side and it started moving, but as mentioned, you stop turning it, it locks up. while its like this it wont start unless i move the crank to ensure its not in the compression stroke, then it would start (intially i had to use a car battery for the extra cranking amps). I thought it would clear after running for a few mins but back to sq 1.

thanks


You've inverted the engine and split the cases, done some work on the bottom end, put it together and the starter wouldn't spin the engine. You barred the engine over by hand and now it spins but only after initial resistance. After approx. 20 second of being left alone the resistance returns. Even with the top end off the same is true.

If that's right, get the bottom off again. You've got something trapped under a main bering shell is my guess. Doesn't need to be much, a piece of tissue or cloth etc. Perhaps you displaced a shell and it's deformed, but less likely.

Actually, just loosening the bottom case bolts ever so slightly might be enough to diagnose.

You didn't zip the bottom case up with a rattle gun did you?
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Pete.
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PostPosted: 08:24 - 07 Mar 2021    Post subject: Reply with quote

Just thinking - did any of the main bearing shells come out? More than one? If you put a thick shell back in where a thin shell came out you might have too little clearance on the main journal.

It's unlikely TBH but it's possible.
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A100man
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PostPosted: 12:02 - 07 Mar 2021    Post subject: Reply with quote

Pete. wrote:


You've inverted the engine and split the cases, done some work on the bottom end, put it together and the starter wouldn't spin the engine. You barred the engine over by hand and now it spins but only after initial resistance. After approx. 20 second of being left alone the resistance returns. Even with the top end off the same is true.

If that's right, get the bottom off again. You've got something trapped under a main bearing shell is my guess. Doesn't need to be much, a piece of tissue or cloth etc. Perhaps you displaced a shell and it's deformed, but less likely.

Actually, just loosening the bottom case bolts ever so slightly might be enough to diagnose.

You didn't zip the bottom case up with a rattle gun did you?


Did similar with a VW aircooled rebuild. Thought it would be wise to use some loctite bearing fit between the shell and the case... it wasn't. I had tight spots so had to disassemble. but that was position related not a time thing which is the curious aspect in this case. With new bottom ends I understand it's fairly common practice to just assemble the crankcase without cams etc and torque up to check free rotation.
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Pete.
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PostPosted: 12:25 - 07 Mar 2021    Post subject: Reply with quote

A100man wrote:
With new bottom ends I understand it's fairly common practice to just assemble the crankcase without cams etc and torque up to check free rotation.


Common practice and good practice. You should always check the crank for free rotation straight after clamping up the mains.

If I follow what the OP has said correctly the starter would not even crank the engine at first and he had to bar it over from the magneto bolt to get some movement. That's a sure sign that something serious is wrong.
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steve the grease
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PostPosted: 17:53 - 07 Mar 2021    Post subject: Reply with quote

Oh well, there's me looking stupid then, I didn't know it was a plain bearing bottom end.
The history is coming out now...

Since that has been established, much sense has been spoken about tight journals , checking , etc, by various people......
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I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....
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jeffyjeff
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PostPosted: 18:45 - 07 Mar 2021    Post subject: Reply with quote

Odd thing, seems the OP would have noticed upon assembly. When turning the engine over to set the valve lash, for example.
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MG#43
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PostPosted: 21:16 - 08 Mar 2021    Post subject: Reply with quote

Thanks again all for the responses!

In response to this from Pete:

"You've inverted the engine and split the cases, done some work on the bottom end, put it together and the starter wouldn't spin the engine. You barred the engine over by hand and now it spins but only after initial resistance. After approx. 20 second of being left alone the resistance returns. Even with the top end off the same is true.

If that's right, get the bottom off again. You've got something trapped under a main bering shell is my guess. Doesn't need to be much, a piece of tissue or cloth etc. Perhaps you displaced a shell and it's deformed, but less likely.

Actually, just loosening the bottom case bolts ever so slightly might be enough to diagnose.

You didn't zip the bottom case up with a rattle gun did you?"


Spot on with the first part, but the top end is not off, cylinder head remains for now with cams removed only, I just feel that i could be needing a new head gasket for a visual check that will show me nothing before i then need to re-open the bottom end. I don't know the general design of bike engines in the stacking of bottom end to top end sections but i know the GSXR's so have a step like design where the head comes apart at the very point the pistons reach top dead centre, so i'd remove the head to look at some piston heads which would not rise about the top of the cylinder block, i turn the crank and will only see so much...this is for now any way....

I agree, i need to recheck the bottom end and track back my steps before anything else, although i was very very cautious and didn't touch anything on or around the crank, other than jigging around the clutch basket, which as already mentioned has been removed to test the issue which remained.

no rattle guns used, just basic ratchet torque applied.
I have already tried removing the bottom end to check another issue around gear selection, I'm less concerned with this, but the issue remained but i didn't look much closer though but i will...

will update again later in the week...!
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Pete.
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PostPosted: 21:49 - 08 Mar 2021    Post subject: Reply with quote

Invert the engine and try to turn it on the spanner. Note the effort required.

Crack all the case bolts in turn and then nip them very gently, just so that each one seats then try the spanner again see if it's any different.

If it is looser, tighten each main bearing case bolt pairs in turn and check the spanner to see which ones make the crank go tight.

If it's no looser after the initial cracking of the bolts, release each main bearing case bolt pair in turn and check every time to see if removing any make the crank go loose. You don't say what year your bike is but on some of the gsxr's the case bolts are mostly M8 but the main bearing bolts are M9. They are five pairs of bolts along the crank from underneath.

If you're lucky this will narrow down the cause/location of the tight crank journal.

In any case, remove the case and inspect the main journals right away. If there's a shiny line around any journal that's foreign matter trapped uner the shell. Inspect the shell, it's probably embedded in the face. If there is, pick it out and put it back together. Test for binding as you tighten each case pair.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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MG#43
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PostPosted: 17:20 - 08 May 2021    Post subject: Reply with quote

An update!!

Sorry took me a couple of months to build the motivation!

So I the engine apart again from the bottom end today to reverse what I'd done, as soon as i removed the mid section of the engine the crank turned even by hand. I had over tightened the bolts causing it to clamp onto the crank shaft. Guessing when it would rotate after lots of force, it was enough to separate the crankcases enough to allow it to spin, then when left it clamped again, possibly some heat/friction would allow it to spin until it settled? either way I'm good with this now...

I wish I'd never gone for the top end as now i have another pain, as the crank gear and bolt were removed and put back without lining either to top dead centre so i need to find another way to get to TDC. These two parts are marked with lines to align to TDC, these lines are now useless until i line it all back up, first time doing cam timing so that's fecking awkward too! but at least the engine isn't toast!! yet..... Very Happy
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Nobby the Bastard
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PostPosted: 17:37 - 08 May 2021    Post subject: Reply with quote

The markings shouldn't be removable from the crank that easily. There should be at least a woodruff key to align the flywheel to the crank.
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MG#43
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PostPosted: 18:21 - 08 May 2021    Post subject: Reply with quote

Nobby the Bastard wrote:
The markings shouldn't be removable from the crank that easily. There should be at least a woodruff key to align the flywheel to the crank.


yeah thanks, I gave up for the day, but next plan was to check if there's something on the other side, but at least the bolt on that side came loose and poss under/over tightened too due to the lock up repeat testing so if its just that i still have issues, assuming it has a line somewhere too Smile
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Nobby the Bastard
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PostPosted: 18:49 - 08 May 2021    Post subject: Reply with quote

If your timing mark isn't fixed to the crank by some sort of locking mechanism you are looking at it wrong or.something is missing.
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MG#43
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PostPosted: 14:45 - 11 May 2021    Post subject: Reply with quote

Nobby the Bastard wrote:
If your timing mark isn't fixed to the crank by some sort of locking mechanism you are looking at it wrong or.something is missing.


thanks, your right, in the end there's actually only one way the starter clutch goes on, the other missing piece was that the TDC mark was on the outer casing which was off the bike so i didn't account for that, bit of poking about on tinterweb taught me to put it back on if i want to line it up! I've sorted the top and bottom end now so we're all done, I can't test as I replaced the engine already... so i'll keep as a spare or sell on... Smile
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