I f***ed up my big bore and now my bike is garbage. - Page 2

ChopperCharles · 04-13-2021, 04:53 PM

I will remove the engine from the frame tonight or tomorrow and begin the task of diagnosing the problem.

If I remove the flywheel, that's just another gasket to replace. It'll tell me that the tensioner is installed incorrectly, but I won't be able to fix it from there, I'll still have to take the head off.

I have drained the oil and inspected the filters. There was a little grit in the right side screen. Not metal, felt like a few pieces of sand or something. No brass in the oil, no water in the oil, and a normal amount of metal on the magnetic drain plug. No metal fragments in the oil (I filtered it) and no metal in the oil filter.

Judging by the oil I'd say it was a healthy motor. Judging by the sound I'd say something is FOOKED.

Charles.

Charles.

Lukas · 04-13-2021, 10:11 PM

It sounds like the valves are meeting the piston there could be two reasons one is a misaligned valve train then the 4th stroke has to be turned twice the other option is a difference in piston height or gasket thickness which causes misalignment and knocking combustion it is good to compare all components before assembly and what is the type of big bore 298?

Charley Brown · 04-14-2021, 02:04 AM

Sounds like you used the wrong feeler gage on the valves make sure it's not standard and that it was a mm gage

ChopperCharles · 04-14-2021, 11:02 AM

Nope, I used the feeler gauge from CSC, and I double checked against my own gauges.

Big bore is the 283cc kit from GPX Moto / Pitster Pro.

Charles.

calvarez · 04-14-2021, 11:59 AM

I can't help on this specific motor as I've never had it apart. However I can say that I've heard a bike with a bad CCT a few times, and that sounds exactly like it.

ChopperCharles · 04-14-2021, 12:03 PM

What's a CCT?

Charles.

calvarez · 04-14-2021, 12:07 PM

Cam Chain Tensioner; on the bikes I've heard sounding like this, the CCT was bad/loose and letting the chain slap around.

grumpyunk · 04-14-2021, 12:20 PM

You should be able to feel a loose or non-working tensioner by moving the cam sprocket back and forth. Of the tensioner has taken up all the chain slack(its job), the sprocket will not want to move freely, even with all valves closed avoiding spring compression effort. It should be locked to the crankshaft sprocket and allow no motion(w/o moving crank).
Removing the tensioner, and then checking cam sprocket motion would give an indication of the tensioner effectiveness.
When removing, there should be spring pressure pushing the whole thing out of its mounting spot on the engine. If there's no spring pressure, it may be the tensioner never 'released' when it was bolted into its position.
tom

franque · 04-14-2021, 01:37 PM

The only problem is that if the front guide isn't installed properly, the tensioner won't be able to properly tension, giving him a false negative on the tensioner.

grumpyunk · 04-15-2021, 02:19 PM

Narrowing the noise to a cam chain is a significant bit of information. The cause, faulty tensioner or possible mis-fitted guide could be discerned further down the road.
Knowing the noise was chain related would be a load off my mind, being something that is relatively fixable and not the end of the engine or a huge hit to the dollar bucket.
tom

ChopperCharles · 04-19-2021, 12:55 AM

Well it’s not the cam chain guide. I took off the stator cover and the bottom of the guide is perfectly in the slot. Which means it’s probably valve to piston contact.

Charles.

grumpyunk · 04-19-2021, 10:12 AM

Do you have access to a USB camera? I bought one on the web to stuff down spark plug holes to look at pistons/cylinder walls. Less than $10, ballpark. Plug into a USB port and see the World! Not really, but you can get an otherwise difficult view(without removing the head). You could see evidence of calve

iston contact.
I just listened again to the two sounds on utube. Has a 'loose' sound to me, as if there was a slinger or similar moving around on the crankshaft, or some washer on the camshaft wiggling around. Difficult to tell sounds using computer speakers, so if there is wailing and gnashing of teeth(piston-valve) that indicates severe impacting going on, the 'power' of the impact does not come through(at least to me).
With the side cover off, can you detect any play or slop in the cam chain? Is it possible the chain is not on the crank sprocket, but alongside it? Being moved by getting jammed between the side of the chain and the crank shoulder?
Was the original head gasket the stamped sheet metal type? The new? If you changed from composite to sheet steel it could change clearance, which you of course already realize.

tom

sebsanch · 04-19-2021, 10:21 AM

Hello Over there!
I' m sure you've already found the solution. But just in case you're still dealing with it , that sounds very similar to a wasted cranckshaft bearing.
That'd be very bad news because you'll need to take apart the whole engine to fix it.

Most of the owners I know around here have had problems with that bearing after 30.000 -- 31.000 km (~19.000miles)
Good luck.

Seba

franque · 04-19-2021, 10:23 AM

Not necessarily... Did you already check compression? Engines with valve to piston contact don't generally run long enough to make much noise. Did you verify timing and everything?

ChopperCharles · 04-19-2021, 12:01 PM

Verified timing like 30 times. It's timed correctly. Both the kit and the bike had stamped steel head gaskets.

Crankshaft was fine before this. Under 4000 miles.

Havent' checked compression, just going to pull it apart.

My guess is that of the two numbers for head bolt torque I found - 28 ft lbs and 50 Nm (37 ft lbs), the former is correct. I torqued to the latter, which may have over-compressed the head and base gaskets, reducing clearance and causing valve to piston contact.

Charles.

04-14-2021, 11:59 AM	#20
calvarez Join Date: Sep 2018 Location: Peoria, AZ Posts: 334	I can't help on this specific motor as I've never had it apart. However I can say that I've heard a bike with a bad CCT a few times, and that sounds exactly like it. __________________ 2016 RX3 2002 Honda CBR1100XX
	0

04-14-2021, 12:07 PM	#22
calvarez Join Date: Sep 2018 Location: Peoria, AZ Posts: 334	Cam Chain Tensioner; on the bikes I've heard sounding like this, the CCT was bad/loose and letting the chain slap around. __________________ 2016 RX3 2002 Honda CBR1100XX
	0

04-14-2021, 12:20 PM	#23
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	You should be able to feel a loose or non-working tensioner by moving the cam sprocket back and forth. Of the tensioner has taken up all the chain slack(its job), the sprocket will not want to move freely, even with all valves closed avoiding spring compression effort. It should be locked to the crankshaft sprocket and allow no motion(w/o moving crank). Removing the tensioner, and then checking cam sprocket motion would give an indication of the tensioner effectiveness. When removing, there should be spring pressure pushing the whole thing out of its mounting spot on the engine. If there's no spring pressure, it may be the tensioner never 'released' when it was bolted into its position. tom __________________ vertical and above ground - my daily goal
	1

04-15-2021, 02:19 PM	#25
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	Narrowing the noise to a cam chain is a significant bit of information. The cause, faulty tensioner or possible mis-fitted guide could be discerned further down the road. Knowing the noise was chain related would be a load off my mind, being something that is relatively fixable and not the end of the engine or a huge hit to the dollar bucket. tom __________________ vertical and above ground - my daily goal
	1

04-19-2021, 10:12 AM	#27
grumpyunk Join Date: Jul 2018 Location: nw of atlanta Posts: 169	Do you have access to a USB camera? I bought one on the web to stuff down spark plug holes to look at pistons/cylinder walls. Less than $10, ballpark. Plug into a USB port and see the World! Not really, but you can get an otherwise difficult view(without removing the head). You could see evidence of calveiston contact. I just listened again to the two sounds on utube. Has a 'loose' sound to me, as if there was a slinger or similar moving around on the crankshaft, or some washer on the camshaft wiggling around. Difficult to tell sounds using computer speakers, so if there is wailing and gnashing of teeth(piston-valve) that indicates severe impacting going on, the 'power' of the impact does not come through(at least to me). With the side cover off, can you detect any play or slop in the cam chain? Is it possible the chain is not on the crank sprocket, but alongside it? Being moved by getting jammed between the side of the chain and the crank shoulder? Was the original head gasket the stamped sheet metal type? The new? If you changed from composite to sheet steel it could change clearance, which you of course already realize. tom __________________ vertical and above ground - my daily goal
	0

04-13-2021, 04:53 PM	#16
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 683	I will remove the engine from the frame tonight or tomorrow and begin the task of diagnosing the problem. If I remove the flywheel, that's just another gasket to replace. It'll tell me that the tensioner is installed incorrectly, but I won't be able to fix it from there, I'll still have to take the head off. I have drained the oil and inspected the filters. There was a little grit in the right side screen. Not metal, felt like a few pieces of sand or something. No brass in the oil, no water in the oil, and a normal amount of metal on the magnetic drain plug. No metal fragments in the oil (I filtered it) and no metal in the oil filter. Judging by the oil I'd say it was a healthy motor. Judging by the sound I'd say something is FOOKED. Charles. Charles.
	0

04-13-2021, 10:11 PM	#17
Lukas Join Date: Jan 2021 Location: A small Polish empire Posts: 244	It sounds like the valves are meeting the piston there could be two reasons one is a misaligned valve train then the 4th stroke has to be turned twice the other option is a difference in piston height or gasket thickness which causes misalignment and knocking combustion it is good to compare all components before assembly and what is the type of big bore 298?
	0

04-14-2021, 02:04 AM	#18
Charley Brown Join Date: Jul 2020 Posts: 1	Sounds like you used the wrong feeler gage on the valves make sure it's not standard and that it was a mm gage
	0

04-14-2021, 11:02 AM	#19
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 683	Nope, I used the feeler gauge from CSC, and I double checked against my own gauges. Big bore is the 283cc kit from GPX Moto / Pitster Pro. Charles.
	0

04-14-2021, 12:03 PM	#21
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 683	What's a CCT? Charles.
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04-14-2021, 01:37 PM	#24
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	The only problem is that if the front guide isn't installed properly, the tensioner won't be able to properly tension, giving him a false negative on the tensioner.
	0

04-19-2021, 12:55 AM	#26
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 683	Well it’s not the cam chain guide. I took off the stator cover and the bottom of the guide is perfectly in the slot. Which means it’s probably valve to piston contact. Charles.
	0

04-19-2021, 10:21 AM	#28
sebsanch Join Date: Sep 2016 Posts: 2	Crankshaft bearing Hello Over there! I' m sure you've already found the solution. But just in case you're still dealing with it , that sounds very similar to a wasted cranckshaft bearing. That'd be very bad news because you'll need to take apart the whole engine to fix it. Most of the owners I know around here have had problems with that bearing after 30.000 -- 31.000 km (~19.000miles) Good luck. Seba
	0

04-19-2021, 10:23 AM	#29
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	Not necessarily... Did you already check compression? Engines with valve to piston contact don't generally run long enough to make much noise. Did you verify timing and everything?
	0

04-19-2021, 12:01 PM	#30
ChopperCharles Join Date: Feb 2018 Location: RDU, NC Posts: 683	Verified timing like 30 times. It's timed correctly. Both the kit and the bike had stamped steel head gaskets. Crankshaft was fine before this. Under 4000 miles. Havent' checked compression, just going to pull it apart. My guess is that of the two numbers for head bolt torque I found - 28 ft lbs and 50 Nm (37 ft lbs), the former is correct. I torqued to the latter, which may have over-compressed the head and base gaskets, reducing clearance and causing valve to piston contact. Charles.
	0