Internal Engine Rattling

Denver Dave · May 26, 2009

Hi All,

I just came from all the threads in the "Vibration" sticky in this forum along with a search and several months of closely following all of the postings to this fantastic resource. I know my problem is not unique, however, the circumstances that led to it have me confused.

I have detailed the problem below but if you want the short of it skip to "The Short of It".

I have an old cruiser with a 50cc motor bolted to it. The motor is ported/polished, has upgraded hardware, made all new gaskets, and is well lubricated. I have 250 miles so far and am loving the experience! During break-in I was very careful to follow the proper procedures and ratios.

After about 100 miles I could feel the boost in power as the rings started to seat and felt comfortable going faster. My top speed on the 16:1 was 30.2 mph with very little vibration and I wasn't even close to hitting the top rpms the engine is capable of.

For the next gallon I went to 24:1 and changed out the spark plug to one of the popular NGKs. I had the same smooth experience and a top speed of 30.7 mph.

Here is where things started to get funny. Once I hit 190 miles I felt a fantastic boost in power and decided it was time to check all the nuts, bolts, and grease everywhere. I remounted the engine the same way I had before but made things more sturdy. I removed the stock chain tensioner and made a new one out of a razor scooter wheel.

The razor scooter wheel was too big for the bracket and would constantly get hung up on the tensioner mounting bolt forcing the chain to drag across it. Since this is my only mode of transportation to work (without having to pay an exorbitant amount for parking) I decided it would do for the time being even though it was causing the motor to bog down and my top speed was only 15 mph. That night I came up with a quick fix to keep the tensioner wheel spinning but the bogging down problem got worse and worse.

Mid-week I went and got everything I needed to use a skateboard wheel as the tensioner. Hooray! The engine ran fine again but once I hit 22 mph it sounded as if was was going to rattle itself apart. I rechecked my mounts, changed plugs, changed gas but by the end of the week the rattle was so bad at any speed I ended up just pedaling home from work.

Over the course of this past rainy three day weekend I proceeded to completely disassemble the engine - all the way down to the point of taking apart the lower and spilling the ball bearings. Since this is my commuter bike I don't want to go past that point until I am confident I have the proper spares on-hand to do so. Everything turned smoothly, no parts fell out, all the gears meshed, and the muffler wasn't clogged (although I cleaned it anyway). There was some carbon buildup on the piston but the plug looked fine so I am assuming it was from the 16:1 break-in mix.

I cleaned, lubed, and reassembled the engine (using new gaskets), every bolt on the bike now has a rubber washer, the engine mount is back to the way it was when I could go 30+ mph with some serious rubber washer action in between, and the engine STILL rattles when I hit 22 mph!?!?!

The Short of It
Engine ran fine at 30+ mph for the first 190 miles
Engine now rattles like it is going to explode above 22 mph
I took it apart
I put it back together
It still rattles above 22 mph

I can understand if this is a crank imbalance issue but why would it run fine for the first 190 miles and then start acting funny? Is there something that can shift in the crank balancing mechanism? Please help.

Dave31 · May 26, 2009

Usually if it's a rattle there is a good chance you have a bad wrist pin, did you notice any sign of the piston hitting the head? Is possible the piston pin is bouncing back and forth on the cylinder walls.

You most likely have the needle bearing type, I would check that first.

Check out Normans total tear down post #7, he is showing the bushing type bearing.

http://motorbicycling.com/f39/bicycle-engine-total-tear-down-391.html

Denver Dave · May 26, 2009

Thanks FR,

The wrist pin is true and held in place with the clips. I did check the bearings/bushing and it was fine. There were no obvious marks on the cylinder wall nor on the head.

I did not specifically check for play in the wrist pin/rod connection but I think I would have noticed something like that while I was turning things over.

Since it looks like it is coming down to it anyways, I will put this on my list of things to double check when I take her apart again.

2door · May 26, 2009

Dave,
Welcome again. If in your opinion everything inside the power producing section of your engine looked good your problem might be in the bearings/gears of the clutch and drive side. While you had it apart did you check the cross shaft from the right to left side of the motor for sloppy bearing fit and how did the clutch/sprockets look? Any signs of abnormal wear or loosness? Don't dispair, we'll figure this one out and get you back running again.
Tom

Denver Dave · May 26, 2009

Thanks Tom, this was exactly my initial thought. The chain was so tight with the razor scooter wheel I thought it might have bent something in there. When i had it apart I did not take the shaft out; I misplaced my gear pulling tool (and of course found it when everything was back together). I thought it was adequate that everything was spinning like a Swiss watch, well okay, maybe not Swiss but spinning smoothly anyways. Also, surprisingly, no wear on the gears - I like to put a little moly in with my grease.

I'll put this on the to-check list as well.

Edit for an additional thought: The engine rattles with the clutch in. Not completely ruling out the whole drive shaft but I thought I would mention that tidbit.

2door · May 26, 2009

Dave,
Any sign of the clutch or gears hitting the inside of the clutch cover on the right side of the engine? Scrapes or scratches that would indicate that there is interference there? As the day progresses more guys will chime in with ideas so hang in there. I'm assuming that when you say "when the clutch is in" you mean disengaged, (clutch lever pulled) If so that rules out a thought I had about chain interference inside the clutch actuator cover, a common problem and a source of noise.
Tom

Denver Dave · May 26, 2009

No housing interference issues.

Hold that thought on the chain issue - I have to make sure it is the same noise when I rev it up with the clutch disengaged. There is a racket - just might not be the same as when I'm moving. I'll clarify after my ride home from work.

Fairracing - after pointing me in the direction of the conrod/bearing I searched far and wide and it really is starting to sound like that might be it. I'll see if I have time tonight to take the top off and check.

Norman · May 26, 2009

do you have the ball and short shaft that goes inside of the main shaft well lubed it can make so terrible sounds. I take the skate board wheel and machine off the outer part of the wheel add a shoulder on each side to the chain has a place to stay in a groove, I also machine the wheel a little bit narrower so it won't rub anything makes a very nice chain tensioner and its very smooth/quiet.
the wrist pin on the bushed rods are very sloppy lots of wobble but it runs the needle wrist pins are on the sloppy side as well. you maybe hearing the cylinder fins vibrating?
I do not use rubber on any of the engine mounts it can make the engine shake more. tight mounts solidly to the frame I use epoxy(5 minute JB weld) to bed the engines to the frame if I can't get a mount to bed completely by sanding it(aluminum motor mount half that's on the engine) using the size of tubing that matches the frame with 80 grit sandpaper wraped around the tubing . I use foam handlebar grips takes out the shake and vibrations.
something else if you run your chain too tight it can cause the main shaft bearing to go bad they will make a racket but when at a stopped position engine running they should not be turningso no noise from them.
did you look under the clutch cover is the star nuts set screw rubbing the cover?
more things to check like the loose bearing in the clutch housing if you take that apart get ready for an easter egg hunt those little bas#### will go to the four corners of the earth and they are hard to find and reassemble I'd check it but not take apart. its a press fit and the more you mess with that the worse it will get.
Norman

Denver Dave · May 26, 2009

Thanks Norman - we're thinking along the same lines here:

Norman said:
do you have the ball and short shaft that goes inside of the main shaft well lubed it can make so terrible sounds.

A bunch of lithium grease with moly added for extra smooth operation.

Norman said:
I take the skate board wheel and machine off the outer part of the wheel add a shoulder on each side to the chain has a place to stay in a groove, I also machine the wheel a little bit narrower so it won't rub anything makes a very nice chain tensioner and its very smooth/quiet.

I used my router and a jig to make a perfect 1/2" slot in the center of the wheel. I also shaved off the excess material from the sides of the wheel so they just barely clear the bearing collars. The thing is very smooth and the chain rides beautifully through it. The next step will be to spring load the bracket.

Norman said:
the wrist pin on the bushed rods are very sloppy lots of wobble but it runs the needle wrist pins are on the sloppy side as well. you maybe hearing the cylinder fins vibrating?

That is on my list of things to check but they didn't look deformed when I had them out this past weekend. The cylinder fins are silenced with some hi-temp silicon adhesive - I'll try and get a sound sample - this is NOT cylinder fin noise - more like a "something came loose in the lower end" noise.

Norman said:
I do not use rubber on any of the engine mounts it can make the engine shake more. tight mounts solidly to the frame I use epoxy(5 minute JB weld) to bed the engines to the frame if I can't get a mount to bed completely by sanding it(aluminum motor mount half that's on the engine) using the size of tubing that matches the frame with 80 grit sandpaper wraped around the tubing . I use foam handlebar grips takes out the shake and vibrations.

After this riding season I plan to weld some mounting brackets to the bike. The same time this problem reared its ugly head I had that sucker bolted so tightly to the frame it could've taken a direct hit from an atomic bomb and not moved a millimeter. Thinking that might be the problem I changed the mount back to the way it was.

Norman said:
something else if you run your chain too tight it can cause the main shaft bearing to go bad they will make a racket but when at a stopped position engine running they should not be turningso no noise from them.

I'll check the noises when I go home (in a half-an-hour YEAH!!!) but you and Tom might be on to something here. Would this happen only at a higher RPM? The bike runs beautifully right up to 22mph.

Norman said:
did you look under the clutch cover is the star nuts set screw rubbing the cover?

No parts rubbing. I have hi-temp silicon strategically placed on the inside of all the covers as well as waterproofing flashing on the outside. None of the silicon on the inside has been torn off or rubbed away and there are no shavings or grind marks.

Norman said:
more things to check like the loose bearing in the clutch housing if you take that apart get ready for an easter egg hunt those little bas#### will go to the four corners of the earth and they are hard to find and reassemble I'd check it but not take apart. its a press fit and the more you mess with that the worse it will get.

Many of your postings are the reason I didn't go that far. I'll try all the peripherals before I chase down tiny ball bearings. I was able to see them while I had the clutch plate off and they were all lined up perfectly.

I'll get back in a couple hours on whether or not I hear the noise with the clutch disengaged. I thought I did but after sitting in front of the computer for nine hours reality tends to blend with fantasy...and insanity.

Thanks for your help!

2door · May 26, 2009

Keep us posted on your progress and discoveries, Dave
Tom

Rockenstein · May 26, 2009

I'm betting it's the wrist pin bearing or the big end bearing...don't take much slop in either one to make a little 2 smoke sound like it's going to grenade at any moment. With the extra load on the engine from the dragging tension wheel you could have stressed them out real good and messed up an already iffy fit.

Denver Dave · May 26, 2009

Well...had a heck of a ride home tonight. Got on the bike and heard a NEW rattling as well as a pinging AND my clutch actuator pin popped out of it's housing.

Turns out my chain guard mount at the engine finally fatigued and my new exhaust gasket blew out. Also, the pin that holds in the clutch actuator fell out.

Note: Rubberized cork makes for terrible exhaust gasket material; smells nice when it burns though.

When I took her apart last weekend and made new gaskets I found the rubberized high density fiber material I got from the auto parts store had hardened and wasn't doing much good sealing anything so I had decided to try something new.

I'm just going to have to break down and send Creative Engineering my next paycheck.

I've spent my free time tonight fixing the chain guard, the actuator pin, and making a new gasket so, needless to say, I have nothing new for this thread regarding the issue at hand.

More in the morning.

Thanks again all! Please keep the ideas coming!

Denver Dave · May 27, 2009

Thankfully it was a fairly uneventful ride in to work this morning.

I got the engine warmed up to operating temps and pushed past the clanking and vibration to see what, if any, noises could be described from the experience. I got up to 24 mph keeping my thighs closer together than they usually are

A funny thing happened; the motor just cut out. No power, no ignition, it just dropped out. It picked back up when I eased off the throttle and ran fine at 18-20 mph but when I tried it again, same thing, just dropped out.

Then it was time for the no-load test; I pulled up to a stop sign and opened her up. Same rattling, clanking, and high vibration up to what I'm guessing was around 6k rpm and she just dropped out. I eased off the throttle and she picked up again. Did that three times with the same results every time - only after the third test it picked back up at a lower rpm.

SO, very curious indeed! This last weekend, to rule out any fuel supply issues, I put in a new automotive fuel line and automotive filter, i ripped out the cheap screen from the petcock, and completely disassembled and cleaned the carb. I have also tested two different plugs and varied the gaps to no effect.

Hopefully this helps with the diagnosis because I'm about ready to just order a new engine.

Thank you all!

Rockenstein · May 27, 2009

Sounds like it leaned out...what's the plug looking like? ie: Black, brown or white

Revving your motor with no load is a bad thing to do BTW...the wrist pin bearing could self destruct without warning and it will make a real mess of your internals.

matt167 · May 28, 2009

I had an old dirt bike ( '78 Suzuki DS-125 ) that did the cut out thing just like that. it locked up at idle shortly after.

Denver Dave · May 28, 2009

Last night I was surprised by a couple free hours, with which, I tinkered

The plug: It looked fine to me; kind of a grayish powdery look. The ground electrode color tone change was right at the 90. The insulator was all the same color with no splatters or rings. Not that any of this would have mattered anyway - the engine runs like a midget with a limp.

The carb: I didn't think it was running lean, perhaps even a little rich, but your diagnosis was sound in theory Rockenstein, so I dropped the needle clip two notches.

The drive shaft: I was determined to remove and inspect the shaft, despite dire warnings from Norman (I had a drop cloth and a magnetic parts plate under the bearing housing at the ready). I pulled the drive sprocket, took off the clutch plate, and took off the bolt. Even with the gear puller I couldn't make that thing budge...any tips?...did I miss something? Anyway, the shaft rotated freely and smoothly albeit a little harder than I would have liked, but not enough to cause the engine to do what it is doing.

The result: The exhaust smoked way more than normal this morning - I'll put the clips back up when I get home. I can't even get past 20 mph now without the engine cutting out and with no load it sounds like about 4500-5k rpms to where it cuts out. At this low range I can't even get to the point where I could hear the rattle. Rockenstein, I wasn't going to go all the way to the top of the rpm range, just to the point where I heard "the noise".

What is left: The next chance I have to work on her will be late Saturday night. I plan on taking her completely apart - every piece. The remaining suspects are the main shaft and/or bearings, the wrist needle bearings, and the crank. I've decided to order a new engine anyway, just to have a spare but hopefully this issue will show itself over the weekend.

Matt, I hope mine doesn't go the way of your Suzuki

ice man kenny · Dec 9, 2018

Denver Dave said:
Hi All,

I just came from all the threads in the "Vibration" sticky in this forum along with a search and several months of closely following all of the postings to this fantastic resource. I know my problem is not unique, however, the circumstances that led to it have me confused.

I have detailed the problem below but if you want the short of it skip to "The Short of It".

I have an old cruiser with a 50cc motor bolted to it. The motor is ported/polished, has upgraded hardware, made all new gaskets, and is well lubricated. I have 250 miles so far and am loving the experience! During break-in I was very careful to follow the proper procedures and ratios.

After about 100 miles I could feel the boost in power as the rings started to seat and felt comfortable going faster. My top speed on the 16:1 was 30.2 mph with very little vibration and I wasn't even close to hitting the top rpms the engine is capable of.

For the next gallon I went to 24:1 and changed out the spark plug to one of the popular NGKs. I had the same smooth experience and a top speed of 30.7 mph.

Here is where things started to get funny. Once I hit 190 miles I felt a fantastic boost in power and decided it was time to check all the nuts, bolts, and grease everywhere. I remounted the engine the same way I had before but made things more sturdy. I removed the stock chain tensioner and made a new one out of a razor scooter wheel.

The razor scooter wheel was too big for the bracket and would constantly get hung up on the tensioner mounting bolt forcing the chain to drag across it. Since this is my only mode of transportation to work (without having to pay an exorbitant amount for parking) I decided it would do for the time being even though it was causing the motor to bog down and my top speed was only 15 mph. That night I came up with a quick fix to keep the tensioner wheel spinning but the bogging down problem got worse and worse.

Mid-week I went and got everything I needed to use a skateboard wheel as the tensioner. Hooray! The engine ran fine again but once I hit 22 mph it sounded as if was was going to rattle itself apart. I rechecked my mounts, changed plugs, changed gas but by the end of the week the rattle was so bad at any speed I ended up just pedaling home from work.

Over the course of this past rainy three day weekend I proceeded to completely disassemble the engine - all the way down to the point of taking apart the lower and spilling the ball bearings. Since this is my commuter bike I don't want to go past that point until I am confident I have the proper spares on-hand to do so. Everything turned smoothly, no parts fell out, all the gears meshed, and the muffler wasn't clogged (although I cleaned it anyway). There was some carbon buildup on the piston but the plug looked fine so I am assuming it was from the 16:1 break-in mix.

I cleaned, lubed, and reassembled the engine (using new gaskets), every bolt on the bike now has a rubber washer, the engine mount is back to the way it was when I could go 30+ mph with some serious rubber washer action in between, and the engine STILL rattles when I hit 22 mph!?!?!

The Short of It
Engine ran fine at 30+ mph for the first 190 miles
Engine now rattles like it is going to explode above 22 mph
I took it apart
I put it back together
It still rattles above 22 mph

I can understand if this is a crank imbalance issue but why would it run fine for the first 190 miles and then start acting funny? Is there something that can shift in the crank balancing mechanism? Please help.

I just had the same problem my friend took and look at my clutch pads and as soon as he looked at my clutch pads the bearings underneath the plate fell out all over the floor he put a new big bubble played in with the bearings and the problem seemed to go away I'm not sure if this is the same problem you're talking about but this is what happened to me thank God I had a friend that could do this because I needed it as my daily ride

ice man kenny · Dec 9, 2018

ice man kenny said:
I just had the same problem my friend took and look at my clutch pads and as soon as he looked at my clutch pads the bearings underneath the plate fell out all over the floor he put a new big bubble played in with the bearings and the problem seemed to go away I'm not sure if this is the same problem you're talking about but this is what happened to me thank God I had a friend that could do this because I needed it as my daily ride

It's called a big bevel plate I think but my words came out wrong anyways that was the rattling in my case the bearings were rolling around when I was driving it and when I was and idle it was making a rattling noise I hope this helps you

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Internal Engine Rattling

Denver Dave

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