VM29 S/Bore Jetting?

[srsupertrap]

So the loud knock was continuing as it ran or did you just hear it at start up only? (I'm hoping the loud noise was just the starter clutch not operating right which will result in a loud noise but most people refer to it as a "CLACK" sound.)

The knocking sound is constant and sounds like it's coming from the lower cases although I have not ruled anything in or out. I looked in the Factory Manual and it details measuring crank pin wear and big end side cleareance but no diagnostic methods.

 

[srsupertrap]

Supertrap, your compression figures are relatively consistent, but on the lowish side. They don't indicate that you have done any top end damage. That knock is of concern though. Have you been hammering the engine at high rpms for a lenghtly period? It sounds as though you may have damaged the bottom end.

I think the compression #'s just rule out top end damage. I honed & reringed this GS back in 2005. One of the local shops told me you lose 15% compared to sea level. No I have not been hammering the engine, based on the throttle position I normally ride well within the Needle Jet & Jet Needle operating range.

 

[49er]

I think the compression #'s just rule out top end damage. I honed & reringed this GS back in 2005. One of the local shops told me you lose 15% compared to sea level. No I have not been hammering the engine, based on the throttle position I normally ride well within the Needle Jet & Jet Needle operating range.

From your description, it sounds like a big end failure.
Use a long screw driver as a stethoscope and place it adjacent to each cylinder against the front of the crankcase, between the headers. You should be able to clearly identify which rod the noise is coming from.
Typically, a big end knock is more prevalent when the engine is under load. When you were nursing the bike home, was the knock quieter than when you were accelerating?
If it is a big end, the question is what caused the failure? Oil starvation and/or over reving are the usual culprits!

 

[KEITH KRAUSE]

You should always work backwards from the main jet. Regardless of your engine's state of tune, the engine's main jet demand will always remain constant in the 3/4 to WOT positions. The only exceptions to this are slight variations in altitude, temperature, humidity or air density.

The size/shape of your needle and the needle jet size will vary according to the state of tune of the rest of the engines modifications. For example, if you wildly port and fit radically timed and/or high lift cams along with a high performance 4-1 exhaust, a stock needle configuration will not allow the engine to operate to it's potential. Under these circumstances, you need to change your needle's configuration and possibly your slide cutaway size, as well.

A rule of thumb starting point for main jet sizing at sea level is, multiply the size of the carbuettor's bore by 4.
Example, if you have a 26mm carb then the maths are 26 x 4 = 104. This is equivelant to a main jet orafice size of 1.04mm.
I am running a 102 or 1.02mm main jet in my GS850 at present. With my engines present configuration, the air/fuel ratio at WOT from 7000 to 10000rpm is 13.3-1.

Well, as I said in my example, sometimes it just didn't work out by doing the mains first. Just made more work, though no big deal. It works for me.
I'm not sure about this formula you mention (carb bore x 4). Are you saying at sea level my bike (26's) should run 104's? The factory uses a 95 main. For my pipe/pods/larger pistons, I run a 138 DJ main which is approx' the same as a Mikuni 130. My bike (and many others here that I've helped re-jet) can handle the larger 142 DJ main at full throttle/high rpm's but often it creates a noticable bog/to serious bog during 55-65 mph top gear roll ons after I know the jet needle is jetted correctly. Going with the 138 eliminated the bog and may cost me a couple mph top end but I'll take real world passing power over a couple mpg off top end anytime. No way would I consider leaning the needle in this situation and trying to make the larger main work.
I'm just saying this is my experience with jetting. If it meant I had to change the jetting sequence to get things right then that's how it went.

 

[49er]

Well, as I said in my example, sometimes it just didn't work out by doing the mains first. Just made more work, though no big deal. It works for me.
I'm not sure about this formula you mention (carb bore x 4). Are you saying at sea level my bike (26's) should run 104's? The factory uses a 95 main. For my pipe/pods/larger pistons, I run a 138 DJ main which is approx' the same as a Mikuni 130. My bike (and many others here that I've helped re-jet) can handle the larger 142 DJ main at full throttle/high rpm's but often it creates a noticable bog/to serious bog during 55-65 mph top gear roll ons after I know the jet needle is jetted correctly. Going with the 138 eliminated the bog and may cost me a couple mph top end but I'll take real world passing power over a couple mpg off top end anytime. No way would I consider leaning the needle in this situation and trying to make the larger main work.
I'm just saying this is my experience with jetting. If it meant I had to change the jetting sequence to get things right then that's how it went.

Keith, the formula gives a ball park starting point. It is erring slightly on the fat side, for obvious reasons. It's only used when running filters. When using low restriction filters or unfiltered velocity stacks, the formula will be too lean.

Mikuni's jetting on the VM's was radically lean anyway. They were tuned to the 4-2 exhaust system, which didn't scavenge as wildly in the lower/ midranges as some 4-1 pipes do. This increased demand is one of the main reasons some tuners struggle to match the right needle shape to their engine's state of tune.

When I dynoed the 850, I also did a series of air/fuel ratio checks at set rpm's. I started at 3000 and went up to 8000, in 1000 rpm increments.
The first runs were with no load on and I noted the AFR's. When a 20% load was applied, most of the AFR's leaned off by one full ratio.


As you say, there are many ways to achieve ultimate performance. In the end, all tuning is a compromise to some degree. The trick is to get as close as possible to your target without greatly compromising performance in the lower or top ranges. You are doing that anyway.

 

[srsupertrap]

From your description, it sounds like a big end failure.
Use a long screw driver as a stethoscope and place it adjacent to each cylinder against the front of the crankcase, between the headers. You should be able to clearly identify which rod the noise is coming from.
Typically, a big end knock is more prevalent when the engine is under load. When you were nursing the bike home, was the knock quieter than when you were accelerating?
If it is a big end, the question is what caused the failure? Oil starvation and/or over reving are the usual culprits!

49er, the knock was most pronounced @ idle. I ride with a full face helmet on and that muffles everything. I drained the oil on Saturday and examined the inside of the oil filter and there was no chunks, debris or anything else inside The oil on the bottom of the pan was not full of glistening metal shaving. That's good. I recruited my next neighbor to listen since he had a cam bearing failure on his 96 H-D. I just asked him to describe what he heard and he though it was knock as well. He used the screwdriver method but we were not successful in locating the sound because the sound transmission. The noise isn't coming from the starter clutch though.

The noise is most prounced @ idle and diminishes as the rpm increase. I was only reving it up to 3000 rpm in the garage. I can hear the noise quite well at the cam chain tunnel which may mean one of the valves lost it's adjustment? I also know the cam chain tunnel would transmit sound quite well from the bottom end.

I am going to inspect the valve train components and check the lash later today. Should have a better idea by tonight.

 

[49er]

49er, the knock was most pronounced @ idle. I ride with a full face helmet on and that muffles everything. I drained the oil on Saturday and examined the inside of the oil filter and there was no chunks, debris or anything else inside The oil on the bottom of the pan was not full of glistening metal shaving. That's good. I recruited my next neighbor to listen since he had a cam bearing failure on his 96 H-D. I just asked him to describe what he heard and he though it was knock as well. He used the screwdriver method but we were not successful in locating the sound because the sound transmission. The noise isn't coming from the starter clutch though.

The noise is most prounced @ idle and diminishes as the rpm increase. I was only reving it up to 3000 rpm in the garage. I can hear the noise quite well at the cam chain tunnel which may mean one of the valves lost it's adjustment? I also know the cam chain tunnel would transmit sound quite well from the bottom end.

I am going to inspect the valve train components and check the lash later today. Should have a better idea by tonight.

From your latest description, it sounds like you have developed the infamous excessive "cam endfloat knock". If so, the engine shouldn't knock until it has reached normal running temperature. The engine won't be harmed by this noise, but it will be a huge annoyance. My 850 used to knock that loud that it sounded like a big end knock at idle, but dissappeared at around 1800 rpm. I did some machining to fix it some 8000 kms ago. It's still as quiet as!
Go to Basscliff's site for the details on the mod.

 

[KEITH KRAUSE]

When I can't hear the noise myself I always suggest checking basics, even if they don't seem like a probable cause.
Are you POSITIVE the cam chain tensioner is working well? Do the factory test and watch carefully. Got the manual?
Also, are you positive that all 4 cylinders are firing well, and the timing/advance is spot on?
If you're worried to start the bike again you can check all the above without starting. The timing and advance timing can be checked statically.

 

[first timer]

did you check you clutch basket as well, these get lose and make a racket as well

 

[srsupertrap]

6/15 Findings

6/15 Findings

When I can't hear the noise myself I always suggest checking basics, even if they don't seem like a probable cause.
Are you POSITIVE the cam chain tensioner is working well? Do the factory test and watch carefully. Got the manual?
Also, are you positive that all 4 cylinders are firing well, and the timing/advance is spot on?
If you're worried to start the bike again you can check all the above without starting. The timing and advance timing can be checked statically.

I have the Factory manual. I pulled the valve cover checked the lash and found the #2 intake was measuring a .006" loose. Andrews Cam Valve lash (.004 - .006" Cold). Replaced the shim and got it back to .004". Checked the slotted cam sprockets bolts and they had not backed off. Checked the Tsubaki Cam Chain & rivet which I replaced long ago; no signs of contact or wear. Yes, I verified the operation of the Cam Chain tensioner. Looks good.

First Timer: over the winter I had Falicon upgrade the Clutch Hub with the thicker backing plate and welded rivets because that thing was rattling like a you know what.

I am going to call Rapidray and get his input. I will reassemble and see what it sounds like.

 

[KEITH KRAUSE]

And you're sure all 4 cylinders are firing well? Sometimes a non-firing cylinder can make some strange sounds.
Any chance of fuel in the crankcase? Enough fuel in the oil can result in knocking. Oil level would be pretty high I'd say. Again, trying to eliminate basic issues first.

 

[srsupertrap]

And you're sure all 4 cylinders are firing well? Sometimes a non-firing cylinder can make some strange sounds.
Any chance of fuel in the crankcase? Enough fuel in the oil can result in knocking. Oil level would be pretty high I'd say. Again, trying to eliminate basic issues first.

Last Saturday I changed the oil after I had it running in the garage for about ten minutes, the oil level was normal and there was no signs of metal shavings in the oil pan as I mentioned earlier. The only thing I touched mechanically over the winter was R&R the clutch hub with the welded Falicon Hub. Last night based on rapidray's sugesstion I pulled the clutch cover and inspected the clutch hub nut. The nut was still tight & torqued. I removed the clutch hub so I could visually examine the two crank throws, no signs of debris. Looked good as the rest of the clutch components so I retorqued everything and reassembled.

I still want to test the oil pump output before embarking on 49er's modification for Cam End Play which is posted on basscliff's website. Essentially 49er states the cams are floating side to side along their axis and the low rpm knock is caused when the cam thrust ring makes contact with the side of lower cam bearing journal. Sound like the same noise I now have.

A VM & DJ Main Jetting Note: I was always wondering about the cross reference between VM & DJ Mains so I measured several VM Main jets with a calibrated Pin Gage Set (Minus series). I posted this in a earlier thread but made a typo; I wrote down a DJ 130 when I actually meant DJ 138. So take a look. Go means you can slip a pin gage thru the inside diameter with no resistance or binding

DJ 138 = .054" Go
DJ 142 = .055" Go

VM 117.5 = .046" Go
VM 120 = .047 Go
VM 122.5 = .048 Go
VM 127.5 = .050 Go

The VM Main are drilled in .001" increments and the same applies to the two DJ mains.

 

[49er]

Last Saturday I changed the oil after I had it running in the garage for about ten minutes, the oil level was normal and there was no signs of metal shavings in the oil pan as I mentioned earlier. The only thing I touched mechanically over the winter was R&R the clutch hub with the welded Falicon Hub. Last night based on rapidray's sugesstion I pulled the clutch cover and inspected the clutch hub nut. The nut was still tight & torqued. I removed the clutch hub so I could visually examine the two crank throws, no signs of debris. Looked good as the rest of the clutch components so I retorqued everything and reassembled.

I still want to test the oil pump output before embarking on 49er's modification for Cam End Play which is posted on basscliff's website. Essentially 49er states the cams are floating side to side along their axis and the low rpm knock is caused when the cam thrust ring makes contact with the side of lower cam bearing journal. Sound like the same noise I now have.

A VM & DJ Main Jetting Note: I was always wondering about the cross reference between VM & DJ Mains so I measured several VM Main jets with a calibrated Pin Gage Set (Minus series). I posted this in a earlier thread but made a typo; I wrote down a DJ 130 when I actually meant DJ 138. So take a look. Go means you can slip a pin gage thru the inside diameter with no resistance or binding

DJ 138 = .054" Go
DJ 142 = .055" Go

VM 117.5 = .046" Go
VM 120 = .047 Go
VM 122.5 = .048 Go
VM 127.5 = .050 Go

The VM Main are drilled in .001" increments and the same applies to the two DJ mains.

Thanks for the confirmation on the VM jet sizes. The numbers actually mimic the size in millimetres, i.e, the VM 127.5 measures 1.275 mm, which in turn equates to .050". I've never had the need to measure any DJ jets as a comparison!

 

[Don-lo]

Supertrap,

First off, nice looking bike! I had a 1000E painted up a lighter shade of your blue, but no cal-fab swingarm, lol. You state there are slotted cam gears, but didn't state the degree(s) the cams are at. Also, what formula did you use to degree the cams? I ask because this is one of the most important elements in getting a GS to idle and transition up.
Also, GS "knocks" are common and often harmless. A small hydraulic lock-up in a high compression engine could do some damage, though. I would check each cylinder by pulling each plug wire and grounding an extra spark plug to the head, then start and run the bike to see if the sound changes when there is no spark to that cylinder. A bad rod bearing or broken piston skirt (I had one of those) will be less noisy without combustion. I have also seen debris wedged into the big gears (crankshaft/clutch hub) that makes a definite knocking noise. Good luck and let us know what you find.

 

[srsupertrap]

6/24 Findings

6/24 Findings

Finally got back to diagnosing last night. First, thanks for all the comments and interest. I warmed up the GS and got it up to operating temperature and as expected the knock returned @ idle up to 2000 rpm. I tested the oil pressure with a new 15 psi VDO oil pressure gauge; the oil pressure was significantly higher when I started but progressively dropped since it was 85 F outside and I recorded 4 psi @ 3000 rpm. The Factory Specification for the GS1000 oil pump is: 1.4 psi < Oil Pump Output < 7.2 psi @ 3000 rpm. Okay.

I have checked and ruled out the following items: 1) Static Timing and # links between cam sprockets 2) I verified the timing with timing light. 3) Cam Chain tensioner operates per the Factory Manual test were you first rotate the crank backwards while backing off the Cam Chain tensioner spring. Next rotate the crank clockwise and verify the tensioner rotates inwards taking up the cam chain slack. 4) Adjusted the #2 intake valve shim to be tighter since the knock is pronounced in that area; all other valve lash okay 5) Per Don-lo?s suggestion, I checked each cylinder by pulling each plug wire and grounding an extra spark plug to the head, then started and run the bike to see if the sound changes; I found no change in the knock location or sound. 6) Per KK suggestion, the spark at all 4 cylinders is excellent thanks in part to the Coil Relay Modification. 7) The cam sprockets bolts were not loose nor had the slotted cam sprockets rotated CW. 8) Andrews 1S Cams are set to 108 C/L angle.

The knocking noise is still most pronounced by the Intake cam. To help determine the location of the sound I employed the long screwdriver method and found the loudest internal noise is actually produced by the cam chain but that isn?t a knocking sound. When I place the screwdriver against the cylinder head by the Intake cam I hear a cyclical knock which isn?t tappet related. So it appears 49er is correct. Next question has anyone performed 49er?s Cam End Float modification stateside and can they recommend a Machine Shop that has successfully performed the modification? My GS has 43.5 K miles.

members.dslextreme.com/users/storagecliff/images/cam_end_float_mod.pdf

Don-lo, the imron paint is twenty years old and the color is 87 IROC Blue. It's due to be repainted, the clear paint under the Gas Cap is lifting. The OEM black paint took a dive while I was stationed at sunny Holloman AFB, NM.

 

[Don-lo]

Yeah, sounds like there are no damaged rod components, so looks to be the cam end float. The mod looks serious enough to leave in the hands of a machinist. If you do it, let us know how much it costs, please.

 

[srsupertrap]

Back on the Road this weekend

Back on the Road this weekend

With the help of 49er, a Machinist at work & $200 I have completed the Cam End Float Modification and hopefully that will eliminate that knocking noise. While I was awaiting parts, I refurbished & repainted my original Master Cylinder as well. When I installed the modified cam caps & half moon washers I degreed the Andrews cams to 108 C/L with zero lash.

Since there has been a lot of discussions on oil coolers I took a couple of pictures last night of my new Parker lines and where I hid the thermostat. The Lockhart BP-180 is located between the frame tube aft of the valve cover oil vent hole.

I like the look of S/S lines but the Parker Push Lok hose is much more flexible and the last set lasted 18 years. I also can also easily remove the valve cover.

I have bumped the VM 29 S/B main to 127.5 from 125 . My fuel filter has also been bent like Nessism and other have noticied.

 

[49er]

Brand new bike.

Brand new bike.

Man that's a sweet looking setup. It's a shame that you have to ride it and get it all dirty!

One other thing, how are you going to fit up your airbox with all that new plumbing around those carbs?

Enjoy your new mods.

 

[Guest]

Holy crap! Nice looking engine! Great work. I've been watching this thread regarding your carb set-up. Since we are at similar altitudes, you're my Guinea pig for when I put the 29's on my project!

 

[Guest]

Where did you find your cam cover bolts? Are those chrome flange heads?