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Discussion Starter #1
So, here’s the run down: 01 stock VN750 (duh), it’s had troubles sometimes on a start up where it would like to rev past 3k, it breaks up pretty bad. Let a buddy ride it the other day while I rode his crotch rocket, and he ran into the problem but kept pushing it, bike eventually died, had trouble started but seemed fine from inside my helmet. When I took it home at the end of the night, it was knocking/clicking/tapping. So in this order, I changed the oil (found lots of glitter in the filter (been about 2k miles since last oil change) but no major chunks) checked compression, adjusted my MCCTs, and the noise has only gone from constant to intermittent at idle, and it’s got good compression on both cylinders, but it still has reduced power and knocks when riding.

so here’s my question/s

what’s the next step to maybe find the cause of the noise, and or fix it?

best place to get a replacement 750?

or (and I kinda like this idea) what engines can fit on the vn750 frame that aren’t a vn750?
 

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Failing dampers can cause them symptoms not needing a engine replacement unless it gets so bad it sends the balancer through the left case. but will need to pull to repair
 

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Discussion Starter #3
What would be the metal in the oil though? I'm thinking I've just spun a bearing and hopefully caught it soon enough that I haven't damaged anything else.
 

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What would be the metal in the oil though? I'm thinking I've just spun a bearing and hopefully caught it soon enough that I haven't damaged anything else.
What color was the glitter? Was it magnetic? Any hard black chunks? Did you check the oil screen or just drain the oil and cut the oil filter open?

Bearing material is usually gold, engine case is silver, broken damper bushings look black, flat gold flakes are usually clutch material, finding small amounts is normal.

A $5 mechanic's stethoscope from Harbor Freight is perfect to pinpoint engine noises.
 

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Discussion Starter #5
No idea if it was magnetic I didn’t even think to check. Glitter was gold/silverfish. Not distinctly either color. When I drained the oil a few nights ago to start the engine removal, there was still more glitter, but it was SUPER fine, and thus color was hard to tell.

all I did to check the filter/s was run some gas through them and shake em out. I never noticed any hard black chunks, just some fine glitter and in the filter some slightly larger pieces, I wouldn’t call any of the material I found “chunks” or “flakes” None of it was substantially sized.


This is a video I took of the oil that had been in the engine during my compression tests, cam tension check, and a 15 minute warmup run to see if I could change the knock sound, or figure out what caused it. That was brand new oil, and was run through the machine for no more than 30 minutes. Looking at that, I’m seeing more silver looking metal? I’m not sure though as I’m unsure how gold bearing material actually is. Hopefully be the end of this coming week, I’ll have the engine opened up, and I’ll be able to see the extent of the damage better.
 

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Really can't see much in the video. How about that oil screen on the left sidecase? Should be able to sample the debris there.

Manual in my signature if you need one.

Is the engine vibrating more than normal?
 

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Probably too late if the engine is apart....

A rod knock gets quieter or goes away when the spark is removed from the cylinder. But in the v-twin, cutting spark on one cylinder reduces the idle by about half, so might need help idling.
 

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Discussion Starter #8
Yeah a little to late now for engine runs, I’ve not removed the engine yet, but all the accessories are off. I cant find the oil screen you reference, is this inside the engine? or external for sampling? I doesn't feel like its vibrating any more than one would expect for a bike on reduced power.


but good(?) news i ran some gas through the new filter that saw only 30 minutes of use (hadn't cleaned it previously as i was just gonna re use it to break in the new engine components) and the glitter i see in there is most definitely gold/bronze in color. so perhaps my prognosis was correct and im just dealing with a failing bearing.

Thank you so much for the replies though, if i happen to break this thing again i now know more of what to look for in trouble shooting
 

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On lower left side of the engine, look for a cap with a 17mm hex on it. Cap about the size of a 50 cent piece.

Screen about 5" long inside, pay attention to how it all comes apart. Cap, spring, washer, screen, and rubber seal.

A pic of the screen content might help.
 

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Discussion Starter #10
panic i thought this was the drain for the oil, and have been using it as such.

Ho-lee-****.... Firstly, my filter is split towards the end, so when i pulled it out i was only able to get so much. Secondly there is SO much debris in there, large chunks,flakes, even some red RTV? mostly bronze/gold flakes a few silver ish here and there and some Gray ish rubber? (it feels like gasket material or seal material as its almost perfectly smooth on the faces but it could be the dampers). I'm starting to think this engine is just absolutely cooked

 

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panic i thought this was the drain for the oil, and have been using it as such.

Ho-lee-****.... Firstly, my filter is split towards the end, so when i pulled it out i was only able to get so much. Secondly there is SO much debris in there, large chunks,flakes, even some red RTV? mostly bronze/gold flakes a few silver ish here and there and some Gray ish rubber? (it feels like gasket material or seal material as its almost perfectly smooth on the faces but it could be the dampers). I'm starting to think this engine is just absolutely cooked

If that's a link to a pic or video, it's not a good link. Says I need access.

Yup, have to be careful with silicone, it migrates, have seen it many times, in funny places a long way from where it was used. The silicone could have starved the bearings of oil.
 

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Discussion Starter #12
I think i fixed the link? But yeah that sounds about right. the dealership I got the bike from just replaced the heads, and rebuilt the carbs so its possible the RTV came from there but I wont know for sure until I actually open up the engine.

Im just hoping I'm not out an engine just yet. Im Curious to start this as a motor swap project, throw a sport bike engine, transmission, and entire drive line on the vn750 frame, so i can get the screaming sport engine, the extra power, maybe fuel injection, but still enjoy the comfortable riding position of the cruiser frame.
 

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Whoa, there's a little bit of everything in there. I think you're going to find some serious damage.
 

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Discussion Starter #14
FINALLY Got the engine out of the frame and began the tear down process. (on a side note are there any simpler ways of getting that damn U joint to disconnent from the engine or the rear end so i can free the engine of the driveshaft easier? I ended up using tiedown straps and pulled frame one way, engine forward and right to get the damn thing out major PIA to do solo and with only a scissor jack)

Found some wear on the chain side of the cam cap and bottom end, Its still smooth as hell to the touch and no substantial material appears to be missing,all 4 cams spots have identical wear on them so I'm pretty much gonna sum that up to chain tension issues causing some minor wear.

Top end looks largely clean both in terms of actual damage and in terms of debris nearby, all drain holes and banjo bolts look clean and clear. no overheating signs on the cams, and the cams themselves show ) signs of damage or abnormal wear. Im currently halted by the goddamn 27mm "Spark plug retainers" that i discovered when trying to remove the front head.
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Spark plug retainers? 27mm? Sounds like you're talking about the plug wells?

The rear axle nut fits the hex on those, and there's another part that works but don't recall at the moment.

If that's not what you meant, let me know.
 

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You may already know, don't mix up the cams, it's a nightmare.

Damage might be at the damper gear, behind the stator case.
 

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Discussion Starter #17
Thankfully ive been marking timing on the chains, marking all parts to fit back where they came, and been cleaning them as i remove them and placing them in a "clean room" away from the tear-down. I got all the cases off, got both top ends and valvetrain off. Question here, is it worth the time and effort to disassemble the valves, clean them and reseat them? I haven't had single issue with them as yet, and as far as i know they seat down just fine, i will be cleaning any and all visible gunk that i can get to I'm just not sure i want to go through the hassle of taking them out and putting them back in.

so far the cylinder walls,valves. top of pistons, and the alternator case seem to be in GREAT condition. both balancer gears have some minor wobble in them, not sure if thats normal. and pictured below is the clutch.It got CHEWED from something.not sure if that was previous owners attempt to hold the part still to remove the bolt, or if that was debris in the case, i havent found anywhere near enough aluminum in the case or the oil to amount for this degree of damage so im thinking it was a previous owner problem. I have found some smaller rubber chunks that were definitely from liquid gasket material that had over flowed into the case. Do you NEED a puller tool to get the gears off? or can i make it by with some elbow grease?

As far as the clutch goes, all the disks were super clean, plenty of pad left, no damage, the inside teeth had super minor dings from what i will assume is normal wear, just the outside of the case is damaged.

52202
 

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Flip the heads upside down, fill the combustion chambers with a thin liquid, gas, alcohol, even water can work but molecules are larger. See if any liquid comes out of the intake/exhaust ports.

Do you see much varnish inside the engine? Varnish on the valve stems can lead to sticky/stuck valves. Leaky and stuck valves dooccur on this engine if let go, or stored, long enough. If it's clean, you make the call. If you don't remove the valves give the stems/springs a good shot of lube, but not a cleaner. You don't want loosened varnish to run down the stems and the solidify while the heads are on the bench. If you leave them in, you can run Seafoam in the oil to clean them later, if they need anything. Depends how it all looks right now.

I will say, some have had sticky or leaky valves right after a teardown. If you have the right spring compressor, it's not too bad, but do one at a time. Just have to get the keepers, locks, back in the right groove.

Even new balancer bushings have a small amount of play in them. Do the bushings appear brittle at all? Just the stator rotor requires a puller, an 18mm bolt. Threads on the left side balancer are left hand threads, and need some blue Loctite going back on. I used a penny stuck between the gear teeth to hold it still. The penny will fold 90 degrees but doesn't hurt the gear. A rag stuffed in there can work also. Pay close attention to orientation of the balance gear and weight, I installed mine 180 degrees off and it shook so badly you couldn't see the hand grips. It wasn't the marks, it was placement of the gear onto the weight. Largest post on the weight goes into the smallest hole of the gear. Pic in the manual.

Really surprised it's in that great shape. Previous owner must have dealt with something. Does the left sidecase look like it's been replaced?

Another item on the valves, a small engine shop may not charge too much to check out valves, since you have the heads off. Very least, fluid check for leaks yourself.
 

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If I missed anything let me know. Editing on my phone just leaves a small slit to read with.

Edit... You say the clutch case is damaged? Where?
 

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Discussion Starter #20
Ah maybe “case” wasn’t the right word for it, it’s in the picture, it’s the clutch itself where all the disks go in, but just the exterior of the clutch, the internals seem pretty healthy to me. Both side cases seem considerably newer than the block. It’s possible they were just cleaned more/better in a previous tear down, but I’ve only owned it for 2k of it’s 18k it’s lived so I wouldn’t know for sure.
 
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