Engine Rephase Rebuild Thread

[alfredo]

So, I am sure a couple of you have been thinking (or taken part in) about a rephase. I have decided, after all the questions and answers on this thread to jump in. My goal is to be able to have a smoother running cruiser. Something that will take me past my current 4.5k vibratory limit. I just want it to be smoother and more of a cruiser without taking too much money. I figured a build thread would be good to show my trials and tribulations. So here we go!

First of all, my motor is less than 2.5k miles since a top end rebuild and 3rd over bore. It has been leaking oil from all over. Have re-torqued and gooped yamabond 'till my hearts content and still my pants get oil all over them. Base gasket, head to valve cover, etc. Tiny leaks, but when you are traveling above 30mph, that oil gets everywhere! I am saying this, because even with no vibrations I would need to break this thing down to fix all those leaks.

Current Specs:
3rd Oversize
fresh top end
boyer ignition
bs38s

Goal Specs:
leave top end alone
delete base gasket
rephased crank/cam
PMA
Pamco
bs34s
Cleaner parts

Beginning:

Got the motor out, in the stand and on the table. Took some wrestling, but was able to yank it out and bear hug it up to the bench. I cut the new wiring to the rotor as I have plans for a PMA.

Some metal in the filter. I replaced both cam guides and I didn't see much black stuff. I didn't tear apart the bottom end when I rebuilt this so I am hoping that some of that metal is from the bottom end, previous internals. Hopefully that is Will know more as we get deeper into the puzzle though.

Got the side covers, clutch basket, kick starter, shift selector, starter bendix and oil pump drive gears all off. I broke a tooth off of the clutch basket while trying to remove it, reached out to the forum for some help and found one in trade from SimpleBob. Thanks again man! Other than that broken tooth, no major damage or missing metal in the gears, case, etc.

Valve cover off. Notice my gratuitous use of Yamabond Prob overkill as it looks like burnt pancakes inside there. Going to have to check and see if the cover is warped as this was a place where leaks were apparent. Not sure how to check for warps other than setting it on a table, but I guess I will learn. Also, springs and tappets all look great.

Cam, lobes and bearings all look great too. This piece will be shipping to Hugh soon. Hoping he works his voodoo for me.

The valves look charred, but seem ok. What does the forum think?

Pistons and sleeves look great too. The sleeves still have 99.9% of the machinist hatch marks in them so I am sure they have a long time to go. Won't be doing anything with these, just putting them back where they were when the rest of this motor is done.

Here is the base gasket. You can kind of see how it is lifted all the way around the sleeves. I can see where the oil just seeped out :/ Going to take Hughs advice and not run a base gasket to bump compression up more and hopefully no longer have an oil leak from this spot.

And here is how she sits now. Going to be trying to squeeze every minute in the afternoons into this thing so I can get it back together soon. I am thinking of replacing the main bolts as I fear some of them are stretched and might be one of the reasons that the seal was never as good as it could have been. Anyone have any input on swapping these? Worth it? Not worth it? Tips, etc?

More to come soon. Feel free to chime in.

 

[littlebill31]

I'm watching this one. Good luck with it. I'm really interested in the base gasket delete.

 

[KentMoney]

I have a few comments now that I am finished with my rephase and I guess this would be a good place to share!

Vibration reduction is probably my number one reason for going with a rephase. I wanted to be able to ride comfortably on long trips and that was important to me. I highly recommend that while you're in there doing the rephase that you get mikes overdrive 5th gear, its essential. Along with that, you need to consider your gear ratios as this is also very important when it comes to reducing vibes at the desired speed. lastly, properly balanced tires can also reduce vibrations noticeably.

I went with the 277 rephase, mikes overdrive 5th, and a 17t sprocket in front and a 32t in the back (520 pitch if that matters). I guess I should also say that I am using the 1st oversize pistons in the original jugs. I find that I can sustain 70-75mpg at 4000-4500rpm and vibrations are pretty tolerable. going above 5000k I do start to get significant vibes and noise. You could probably get a higher and more comfortable cruising speed than me with a gearing change, because I made a compromise to try to maintain good acceleration in the lower gears for city riding. I think the 5th overdrive saves me here.

I also have had a little bit of oil leakage but I have always been surprised to find that my pants were always clean. It didn't help that my bike got dropped about 5 times off the stand, probably tweaking the motor, but considering that it's doing OK. I did the engine breather modifications like drilling out the hole and baffle and also getting the check valve. I've never ran my engine without those mods so I can't compare, but maybe it'll help out your problem? I think you're not supposed to cake on the yamabond, so maybe go easier on that next time? and make sure you clean the mating surfaces well.

 

[alfredo]

I have a few comments now that I am finished with my rephase and I guess this would be a good place to share!

Vibration reduction is probably my number one reason for going with a rephase. I wanted to be able to ride comfortably on long trips and that was important to me. I highly recommend that while you're in there doing the rephase that you get mikes overdrive 5th gear, its essential. Along with that, you need to consider your gear ratios as this is also very important when it comes to reducing vibes at the desired speed. lastly, properly balanced tires can also reduce vibrations noticeably.

I went with the 277 rephase, mikes overdrive 5th, and a 17t sprocket in front and a 32t in the back (520 pitch if that matters). I guess I should also say that I am using the 1st oversize pistons in the original jugs. I find that I can sustain 70-75mpg at 4000-4500rpm and vibrations are pretty tolerable. going above 5000k I do start to get significant vibes and noise. You could probably get a higher and more comfortable cruising speed than me with a gearing change, because I made a compromise to try to maintain good acceleration in the lower gears for city riding. I think the 5th overdrive saves me here.

I also have had a little bit of oil leakage but I have always been surprised to find that my pants were always clean. It didn't help that my bike got dropped about 5 times off the stand, probably tweaking the motor, but considering that it's doing OK. I did the engine breather modifications like drilling out the hole and baffle and also getting the check valve. I've never ran my engine without those mods so I can't compare, but maybe it'll help out your problem? I think you're not supposed to cake on the yamabond, so maybe go easier on that next time? and make sure you clean the mating surfaces well.

Just to be certain, you are saying that after you did a 277 rephase you still have significant vibrations above 5k? I believe you if you say that, just that it goes against everything I have read. Good to hear this kind of input.

 

[retiredgentleman]

alfredo;

If you did the top end rebuild, you need to read the "Leakless Assembly". Cleanliness, and torquing/retorquing are super important. You should not have that carbon build up, with such low miles on the engine. Looks like you had head gasket passing oil right from the fresh rebuild.

http://xs650temp.proboards.com/index.cgi?board=EngineModified&action=display&thread=327

 

[Punkskalar]

Upon rebuild, make sure ALL your mating surfaces are clean, clean, clean!

AND, what torque did you use on the head bolts on your first build? I torque to 35 Ft. Lbs. on all my XS builds, and rarely ever get a leak from head gaskets or base gaskets.

Deleting the base gasket will be nice, you'll need to redegree the cam to work with it, nothing we can't do at the shop, or via online help. We've done several "stock" engines with a deleted base gasket, they run very well. Again, CLEAN mating surfaces to avoid leaks. And use some good seals, from Yamaha, don't mess with the seals from anywhere else...

Let me know when you are headed this way, can't wait to meet ya

 

[blackbetty]

You should also consider doing a copper head gasket...

I'll be watching this, love your build man.

 

[Punkskalar]

You should also consider doing a copper head gasket...

I'll be watching this, love your build man.

Or one of those new MLS gaskets from Ottoco, I just installed one on my latest engine build. Nice stuff...

 

[KentMoney]

yup. what have you read? up to what RPM should vibrations be minimal?

I will pay attention the next time I ride, but I'm pretty sure I'm remembering correctly...


and regarding the base gasket removal, you say that the cam needs to be advanced by 4 degrees? This is about one cam sprocket tooth, right?

 

[alfredo]

alfredo;

If you did the top end rebuild, you need to read the "Leakless Assembly". Cleanliness, and torquing/retorquing are super important. You should not have that carbon build up, with such low miles on the engine. Looks like you had head gasket passing oil right from the fresh rebuild.

http://xs650temp.proboards.com/index.cgi?board=EngineModified&action=display&thread=327

Any tips on removing the carbon build up without messing up the surface? Just some fine steel wool and penetrating fluid maybe?

Upon rebuild, make sure ALL your mating surfaces are clean, clean, clean!

AND, what torque did you use on the head bolts on your first build? I torque to 35 Ft. Lbs. on all my XS builds, and rarely ever get a leak from head gaskets or base gaskets.

Deleting the base gasket will be nice, you'll need to redegree the cam to work with it, nothing we can't do at the shop, or via online help. We've done several "stock" engines with a deleted base gasket, they run very well. Again, CLEAN mating surfaces to avoid leaks. And use some good seals, from Yamaha, don't mess with the seals from anywhere else...

Let me know when you are headed this way, can't wait to meet ya

Said good seals, where does one purchase these from? I am about to make a Mikes order, but loathe the Athena gaskets. Also, any thoughts on what KentMoney is saying about big vibes on a rephase?

You should also consider doing a copper head gasket...

I'll be watching this, love your build man.

Thanks man! Will definitely weigh the options.

 

[mrriggs]

The re-phase still vibrates. It's more of a buzzy vibe than a throbbing vibe. I actually prefer the stock vibration.

 

[Jack]

I have a few comments now that I am finished with my rephase and I guess this would be a good place to share!

Vibration reduction is probably my number one reason for going with a rephase. I wanted to be able to ride comfortably on long trips and that was important to me. I highly recommend that while you're in there doing the rephase that you get mikes overdrive 5th gear, its essential. Along with that, you need to consider your gear ratios as this is also very important when it comes to reducing vibes at the desired speed. lastly, properly balanced tires can also reduce vibrations noticeably.

I went with the 277 rephase, mikes overdrive 5th, and a 17t sprocket in front and a 32t in the back (520 pitch if that matters). I guess I should also say that I am using the 1st oversize pistons in the original jugs. I find that I can sustain 70-75mpg at 4000-4500rpm and vibrations are pretty tolerable. going above 5000k I do start to get significant vibes and noise. You could probably get a higher and more comfortable cruising speed than me with a gearing change, because I made a compromise to try to maintain good acceleration in the lower gears for city riding. I think the 5th overdrive saves me here.

I also have had a little bit of oil leakage but I have always been surprised to find that my pants were always clean. It didn't help that my bike got dropped about 5 times off the stand, probably tweaking the motor, but considering that it's doing OK. I did the engine breather modifications like drilling out the hole and baffle and also getting the check valve. I've never ran my engine without those mods so I can't compare, but maybe it'll help out your problem? I think you're not supposed to cake on the yamabond, so maybe go easier on that next time? and make sure you clean the mating surfaces well.

When rephasing,the optimum balance factor would be 50% and 65% for the standard firing. Heavy pistons,pins and rods or re-balancing to achieve the 50% = a smoother running rephased engine

 

[alfredo]

I guess the main reason for doing the rephase is to dramatically reduce vibrations. If you check the thread I mentioned in the top of this one you will see I got good feedback on the positives of the rephase. I think I am now second guessing if the vibrations after a rephase are bad enough to make at least one forum member prefer the original vibes. But, with that said: circumstances could be vastly different. So. I guess we shall see.

 

[KentMoney]

don't have doubts about it man. just do it! I don't think you'll regret it.

another thing I just thought about... I don't know what pipes youre running but open pipes can very much contribute to vibes and to general fatigue from all the noise. Every pop outta those open pipes sends a shockwave through your bike. consider a good exhaust setup with a muffler. this is gonna be the next change I make to my ride..

 

[mrriggs]

I did the re-phase solely to get the sound of a 90° v-twin, not to reduce vibration. I liked the vibration of the stock motor. The pounding vibration is what gives old bikes their character.

If you do not like the stock vibes then by all means try the re-phase. The vibes are less intense but more buzzy than rhythmic. Just don't expect it to be smooth. It is a parallel twin with no counter shafts, no matter what you do it is going to vibrate.

 

[irristeve]

They dont call em 650 dildo's for nothing, my 750 rephase still vibrates,but you won't be disopointed with rephase,noise & tourqe is good,go for it

 

[bdholsin]

They dont call em 650 dildo's for nothing...

Big like.

 

[alfredo]

I was wondering how long it was going to be until the word dildo showed up on this forum. It is valentines day after all.

 

[Punkskalar]

On any solid mounted engine, you are going to get some vibes. With a cut down bobber/chopper/brat/cafe' -etc, you are removing alot of items that help to cut down on vibes as well. The rephase is the smoothest possible running configuration for an XS650.

With a stock bike, with thick seats, rubber mounted everything (any rubber at all on the chassis, even side cover grommets) you don't notice the vibes, as the rubber is helping to absorb some of it. But, when you get rigid mounted pegs, thinner seats, the vibes have to go somewhere.

Jack is correct, the heavier the pistons, the smoother the engine will run. JE and Wiseco pistons are pretty stout, and cut down on vibes nicely. The Heiden Tuning Pistons are fairly lightweight in comparison.

And with ANY XS650 engine, a proper tune is critical to reduce vibes. The last non-rephased bike I rode, was the "Father In Law" chopper I built, and I rode it about 1200 miles in a long weekend. I thought I was gonna toss it into a lake, it shook soo bad above 4500 RPM that is was just about unbearable. The tune was good, and it had a shell cam in it, and it just shook the guts out of me at interstate speeds, and then on the back roads I couldn't ride very aggressively without getting into those upper rpms.

As a comparison, my black and white bike (see my profile pic) is WAY less comfortable than the chopper was. The Black and White bike has a more aggressive riding stance, whereas the chopper was a big comfy couch. But I can ride the Black and White rephased bike for a week solid, with solid aluminum hand grips, solid riser bushings, solid mounted aluminum pegs, etc.. and not feel as fatigued and worn out. The vibes are soo much less noticeable, and that makes the bike that much more enjoyable to me.

That is just considering the vibes, take into account the ability to ride harder, longer and get a flatter torque curve, and you really have a fun bike with a rephased engine.

Everyone has their preference, I don't have to be a salesman for the rephase, people just love em' - but other love the jackhammering, walking backwards down the driveway, stock configuration as well -

 

[littlebill31]

...walking backwards down the driveway, stock configuration...

How did you know my bike escaped yesterday?!