Cam chain tensioner popped out on the highway....is my engine toast?

[herennow]

How much are new pistons going for in the us?

[Bluesmudge]

How much are new pistons going for in the us?

$80 each. So $160 for the pair.

Things got even more complicated today as I tore into it more.

-I have 2 sets of cylinders. Both have some scoring that I can catch with my fingernail and one has a decent pit in it, so no good based on the little I know about engines. I had already ordered the standard size pistons and rings, so rather than move to the oversize Suzuki pistons and have the cylinders bored out, I sprang for a new set of cylinder jugs on eBay. Pretty expensive at $450,  but still cheaper $200 than Partzilla charges and I figure I'm in so deep at this point I might as well have a "new engine." I'll have brand new cylinders with factory cross hatching to mesh with the new pistons/rings.

-But then things got more interesting. I should heave checked this first, but I hadn't noticed that the rear cam chain tensioner guide was very worn out and had a chunk missing from it. Of course this is the one guide that can't be replaced from the top end. So now I have to remove the engine and split the case to replace a $35 cam chain tensioner guide. I've never removed the GS engine before,  or messed with the bottom end of any engine. I imagine removing the engine will be much easier since I already have the top end off.  Then the question is...do I rebuild the top end off the bike, or return the bottom end to the bike and then build the top end there. I've seen/heard its pretty difficult to slide the full engine into the frame.

This is turning into way more of a project than I expected. At this point half the reason I'm fixing the engine is for the learning experience, since after buying all these parts I'm getting close to the price of a decent used eBay engine.

[herennow]

Getting engine back in frame is easy if you know how. slide it in at 90 degrees to normal and then turn it forward  once its almost in place. Ive got pictures somewhere, I know this was a revelation for me after struggling for hours. 

I dont remember the bottom end7 gearbox being very hard to get back together. I'll double check my notes and post some pictures.

I remember that removing the heads and cylinders leads to gunk around the studs falling into the bottom end....

[The Buddha]

That rear cam guide is a dumb effing design. I've trashed many a motor at the sight of that damage.
Cool.
Buddha.

[Bluesmudge]

I have made some good progress on my rebuild.

I got as far as splitting the cases and replacing that cam chain tensioner guide. While I was in there I replaced the input and output shaft seals, the shift shaft seal, and put in a complete output shaft/bearing assembly from a lower mileage bike (16k vs 55k) because my output shaft splines were pretty worn from accidentally running a front sprocket with the shoulder faced the wrong way for a long time. I got it pretty cheap off ebay. I would have never replaced the output shaft otherwise, but since I'm there...

Started putting it back together. It took my a really long time to learn how the transmission works and to test to make sure I put it back together right and shift through all the gears. You can't really test it like you are used to on the bike until you get the shift assembly all back on. Then I couldn't find neutral and had to learn how the little wheel with removable pegs is the "neutral finder" and I had to move the neutral peg to where it now needed to be to engage neutral in the right spot between 1st and 2nd gear (something must have gotten out of alignment when I removed the output shaft so hopefully my neutral light still works after moving that little peg). I can now shift through all the gears as expected, including neutral.

The oil screen and sump cover is back on. Now its just oil pump, starter motor, clutch, and generator rotor to go back on and I can start rebuilding the top end like I originally intended. Or I might rebuild the top end off the bike and put those parts back on once the engine is in the frame since many of them require a lot of torque which could be hard to do with the engine on the bench.

[herennow]

good to hear, keep up the good work, some inspiration from my rebuild 10 k km ago...

[herennow]

last one, and here is the bastard cam chain guide....

[Bluesmudge]

Nice photos. That all looks too familiar now, although your engine looks much cleaner. Interesting that you didn't have to remove the starter clutch/generator assembly. The instructions said it was required but the instruction always to it the 'right' way and never the easy way.. Would have been nice to have one less thing to remove and re-install.

Did my description of the gear change neutral cog thing make sense? Does it sound like I did it right? I wasn't sure if it was okay to move those pegs to get neutral acting correctly. Its not described well in the Haynes manual, it just says to study how it works.

I didn't do the plastigauge thing since that wasn't the reason I was in the bottom end. If I was confident in my ability to assess and replace big end bearings, then I would have done it but I'm already way out of my depth here. I just wanted a cam chain tensioner guide that didn't look like a dog's chew toy.  I'll be happy just to have a running back after all this is over.

[herennow]

Im sure it will work fine, I'm sorry I do not recall the neutral sensor.

I took a huge chance and just got new crank shell bearings and sized them based on plastigauge readings before and journal micrometer measurements. HAd a huge excel sheet, worked out in the end. Loved buying the japanese precision parts.

My old britbike parts really seem agricultural in comparison....

[Bluesmudge]

I just picked up my re-worked head from a local machinist. I gave him the low mileage head that came from a 2001 that ran out of oil and lost the bottom end. I figured it had 50,000 fewer miles and 4 good valves so it was worth risking the unknown history. He said everything look fine, like the top end had enough oil to survive. He cleaned everything up with a "multi angle valve job that's better than factory spec." New valve seats and viton seals that should survive better again ethanol gas. I blocked off the mechanical tach port since I'm putting this '01 head into my '06 bike.

New pistons, wrist pins, circlips, and rings are on the engine and looking good. Next up I'll drop in the new cylinders and assemble the top end and set the timing and valve clearances.  I'll get this done eventually. And it might even run when I'm done.

[herennow]

Cool, getting there. Sounds like you are not far away.

I'm slowly building up an old triumph and it's taking its time also as life gets in the way. Hoping to hear it roar before winter though!

[Bluesmudge]

Thanks for following along. I'm posting mainly to keep myself sane as I slowly rebuild this engine and bike.  I get to work on it at half hour or sometimes hour long intervals fit in between everything else life says is more important than my GS500 getting back on the road.

I snapped the oil pump gear while reinstalling the clutch basket. The instructions mention making sure the gears mesh with the crank cog's teeth but don't mention the less obvious oil pump gear that sits behind the clutch basket. there was a very loud cracking sound when it cracked as I was torquing then main clutch hub hit and I thought I had broken something serious. Luckily it's a pretty cheap part on eBay and I was able to get a low mileage one for $16. Another little bit of learning on this project and yet another part from some random salvage yard GS500 with far fewer miles than mine. At this point only the bottom end of of my engine is original to the bike and even that has a new used output shaft.

With the new oil pump cog I was able to get the clutch installed and button up the right side of the engine. A few days prior I put the top end on with a new cam chain tensioner and set all the valve clearances. Almost ready to go back in the frame!

[Bluesmudge]

A month later and I have the engine back in the frame and have officially started the bike! I was hoping this would be the end of this saga, but the bike runs like horrible sh!t. I was able to put a few miles on the bike, but it needs to be dialed in before it can be thought of as reliable transportation again. Seems like a carb/air issue, which is weird because the carbs were very dialed in before the bike broke down.

Starting cold with choke, the bike only revs to 1500 rpm instead of 4,000. Once warm it will hold 1200 rpm nicely with no choke. But the revs are slow to return to idle and I have a lot of flat spots, buzzing, and hollow sounding exhaust/intake note through the rev range. The revs drop below the idle point after a rev and then return to 1200. If I blip the throttle a few times in a row I sometimes get mild backfire through the carbs. At higher revs the tach needle seems to be jumping around as the bike is running rough/buzzy. Almost like it's running in one cylinder but both exhaust pipes get hot right away and the 2004+ bikes don't lose spark on one cylinder, it's both or nothing. Also both spark plugs look exactly the same: black/sooty except the curved electrode part which is ash white. This implies both cylinders are running and doing the same thing, because they look the same and both plugs were brand new. If one cylinder actually wasn't running that plug would look new. The sooty plugs make me think it's running rich, but I'm always skeptical of plug pulls to tell you much. But the idle drop after revs is also supposed to be rich running behavior.

The air mixture screws do almost nothing. It runs almost as well with them screwed all the way in as with them 4 turns out. Slightly better all the way in or .5 turns out than with more turns out. It does start to run bad after 4 turns out and it won't run with the mixture screw removed,. I confirmed the o-ring and washer and spring are in there, the mixture tip isn't damaged and the o-rings look plump. If I was tuning an old bike that was new to me this would make me think the pilot jets were too big, but I know this bike and the  pilot jets are the stock size of 17.5, which was working great before the bike broke down (confirmed with a dyno run after the shop rebuilt the engine in 2020).  This made me think that maybe there was an air or vacuum leak pulling too much air past the pilot and choke circuits, which also pulls more fuel to make it run rich? My ability to diagnose CV carbs is being stretched to its limit.

I checked the vacuum balance on both carbs, they were almost exactly the same already so required no balance adjustment. The valves were just set with the rebuild.

The carb to engine boots and o-rings are new.

I did a very general spray of wd40 and carb cleaner around everything and found no change in revs.  Also tried pushing the carbs around and moving/squeezing the vacuum line to see if revs changed and there was none. That doesn't mean 100%  there isn't a leak, but the carbs got fresh rubber bits in 2020 when the bike was rebuilt by the shop, so carb internals are only 3 years old.  Fuel lines and half the vacuum line are brand new and the bike ran great before it broke down.

With the air filter removed I confirmed the action of both slides. They seemed to vibrate up and down when throttle was applied and the revs got choppy. Especially the right slide  I don't know if that's normal with the air filter removed or indicative of the problem, like a vacuum leak I still haven't found.

I might have found the problem when I removed the air filter to look at the carb slides.  The metal bottom of the foam uni filter had come partially unglued and was probably letting a lot of additional unfiltered air into the air box. I tried taping it back together while I wait for a replacement but that didn't seem to  fix the problem, but I'm just going to wait for a new filter before trying to diagnose any further.

If a new air filter doesn't fix the issues I'll check fuel height. There was a moment when my temp fuel tank was off and the bike was running that the choke acted correctly by jumping up to 4,000 rpm instead of 1,500 rpm. So the bike seemed to like running low on fuel in the float bowls (again confirming that it's probably running rich for some reason). But I don't want to bandaid the problem by lowering the fuel level if that's not the actual problem, so if fuel height is correct  then I'll start dismantling the carb for cleaning. I was hoping the carbs would work as good as the day the bike broke down because I'm pretty sure I drained the float bowls not long after the bike broke down and I also usually put in ethanol free gas but it's still possible there was some fuel in there to gum them up these last 8 months. I don't know carbs well enough: is it possible that a clog somewhere could make it run rich at idle and bad through the whole rev range? I'm pretty sure the only thing that effects all throttle positions is the fuel height and the float needle/valve. The carbs were stored upside down on the bike sometimes while I worked on it. I wonder if that could have messed up the float position or float valve function?

[Bluesmudge]

I got things pretty well dialed in now. I had broken one of the vacuum nipples on the white doohickeys on the carb tops on my 2006 carbs. I replaced both carb tops with ones from an '01/'02 bike (same as gen1 SV650). See my other post about it. It really cleans up the '04+ carbs and seems to have fixed a lot of my tuning issues. For a lot of the rev range the bike seems to be running better than ever.

The new carb tops plus a new OEM air filter seems to have fixed my issues. I just have a really big dead spot if I do a fast WOT roll on while cruising on the freeway. I hit a big dead spot around 6000 rpm with WOT. If I roll on slow using mid throttle it doesn't happen. I'm probably jetted way too rich for the OEM air filter since it was set up on a dyno for the Uni filter. I'm not sure if it's the main jet or the slide needles causing the issue.

I'll probably eventually try and tune it a little more by either going back to the Uni air filter or swapping out all the jets and needles back to OEM but for now it's nice to just finally be able to put some miles on the bike. 50 miles so far. I'll ride it another 50 and change the oil for the first time after the rebuild. The original Suzuki break in was 600 miles but that feels like a lot of miles after my fresh amateur rebuild. I want to get any metal shavings out of there.

The good news is that a lot of the secondary little things I fixed up while doing the rebuild has the bike really feeling fresh. New chain/sprockets. New clutch springs with a 3 point clutch adjustment. New rubber gaskets on the speedo/odometer. New output shaft so the front sprocket doesn't have excessive play anymore, new left handlebar control so my turn signal and horn controls don't stick anymore.

[Bluesmudge]

The bike still isn't running quite right. Its totally rideable but a little funny.

Choke only brings RPMs up to 1500 or so but it starts reliably. Choke has to stay on for awhile. Like 5 minutes. The bike used to only need choke for 30 seconds or so. I think its normal to need choke that long but the rpms should be up around 4,000 with full choke.

Once warmed up the idle will drop below 1200 rpm coming to a stop, implying the bike is rich. But adding any more turns to the mixture screw makes it run worse, implying its not. My Stainless Steel headers look a little bit blue which I think is new, implying its a little lean.

I have a very lightly hanging idle, which is also usually a lean condition. It feels like I have almost no engine breaking. Can't lower the idle any more or the bike will die coming to a stop. Mixture screw was already adjusted for highest and best idle.

I'm guessing I need to clean the carb. Maybe some small areas like the choke passage got gummed up before I drained them. That's the only thing that changed about the carbs, which were working great otherwise. I guess I'll order some o-rings and gaskets so I can freshen things up while I'm in there. So much for my pride in never having cleaned a set of GS500 carbs before.