Vibration is driving me insane... guess my vibration?

[drewpy]

you can get the bearings resprayed with the white metal if you are having trouble getting them. although yamaha top dog will surly have some in stock. there are generally 3 sizes in colour ( black, blue and ?)

I generally use the black ones and I'm sure they share the same part number with another modern yam bike. I'm at work atm so don't have full access to everthything. I' positive its been mentioned in this forum.

get the part number from yamaha online/cmsnl) and google it

 

[Drewcifer]

Taking an engine apart is not difficult, but the diligence of separating and labelling the screws and bolts, and taking the photos to use to reassemble means you need to pace yourself. Working on it focused maybe no more than 2 hours a day, you can easily do it. The patience in labelling and organizing and most of all taking pictures pays off a month later when you put it back together. You will NOT remember anything at that point.

Get a lot of parts bins and peel and stick labels, sharpies, silver paint markers, and go slowly and patiently. It is not difficult at all, just requires FOCUS.

 

[bcware]

I'm still trying to figure out the best tool to measure the microscopic clearances of the crank and big end of the rod...

Plastigauge. http://www.plastigaugeusa.com/

If it costs 200-300 to do a rebuild yourself I'd consider a new motor; it may only be a little bit more money. I've seen plenty of complete parts bikes for that kind of money with good motors.

 

[Drewcifer]

I agree with BC.

The reasoning is as follows. To get at the valves, you have to remove the head. That usually means you ought to level the head at a shop and put in a fresh head gasket, so there's a 100 dollar bill gone easily. Now you have to pay to reseat and replace the valve seats and valves, another 100 dollar bill gone.

That is the Cheapo version. With the head off you can also remove the cylinder bore and have it honed and checked for wear and warpage. That's another 80 bucks. We're at 280 now and we haven't even DONE the cams. And this is without labor. This is costs for DIY.

Then you get the plastigages and measure the bearings (they are "bearings" as in something rotates in them, not circular bearings like ball bearings, for those that have never done this before) and you may or may not need to replace a cam bearing or the cam shaft. Another x? amount of dollars.

Now when you were done with all of that, you'd have a nearly new, nearly perfect motor in many respects. And the experience of doing it yourself. Invaluable, and confidence building.

But a running motor with a good 20,000 more miles in it might be avail to you locally for 100 or 200, and with a friends pickup and a greasy afternoon, you'd have it installed already, and running.

That's why we all sort of sigh when we think the bike needs a TOP END JOB. It can mean engine replacement time might be near, and less expensive.

Hope you guys got something from that. Good look to you buddy.

Drewcifer

 

[devdg]

Plastigauge. http://www.plastigaugeusa.com/

If it costs 200-300 to do a rebuild yourself I'd consider a new motor; it may only be a little bit more money. I've seen plenty of complete parts bikes for that kind of money with good motors.

Plastigauge is used to tell you if the clearance between the bearing and the rod journal are within spec, this will not tell you if the rod journal will need to be turned to 10 thou under or 20 thou under. Only a outside mic will give you that information

Regardless of the engine, anytime you need to think about removing the rods and pistons the heads have to come off. I have never rebuild one of these engines but I will assume the cylinders need to come off to split the case to get at the crank to measure the rod journal.

It would be cheaper to buy a used engine and run it but how long will that last? did the PO change the oil regular? and the types of questions you need to ask. A rebuilt engine gives you the current owner the chance to make it out live your riding days.

Budget will determine what you do in the end. If you have the money and time, a rebuild is a good way to go but if you don't then a used engine will get you going quick.

 

[Scorpio1963]

Just use roller bearing rods from a xs650

 

[devdg]

Just use roller bearing rods from a xs650

will those fit? I have a spare set kicking around someplace

 

[Scorpio1963]

i beleive the journal size of xs650 is larger in diamater than of the xs400.One one way to make it work would be to have your crank welded up and then reground to size.If $ isnt an issue you would have a very high reving xs400.You would probaly need to have the rod sides shaved down to remove excessive weight.Anything is possible if the $ is there.Edit I think the xs650 rod is also longer than the 400.
It would probaly be easier have a custom bearing made for the xs400 rod.

 

[Scorpio1963]

Just what i thought Direct from google
Can you use this connecting rod in xs400 The Garage. ... No xs650 rods won't work in a xs400 much longer and thicker. ... stroke than the 400xs,is there a crankshaft that has a shorter stroke that can be used to compensate for
As i mentioned it would be more feasable to custom make a roller bearing for xs400 rod.

 

[devdg]

I would also assume our crank is forged not manufactured like the 650.

 

[Scorpio1963]

Im not sure,I tryed looking it up but couldnt find any info.

 

[CrazyCabbie]

Hehe, thanks for all the information guys, now I have a better idea what I'm getting myself into.
Thanks for the tip on getting the bearings resprayed drewpy! I wouldn't have thought that was possible.

I've formulated a plan now, thanks very much to another forum member... swap and rebuild!
(that's the PLAN anyways...)

I have a spare engine coming hopefully Friday, so I can enjoy my summer! Yay!

However, I REALLY like this bike, and the possibility of riding it 'forever'... I get great satisfaction repairing things myself too.
This way instead of attempting a 'pit-stop' rebuild, I can collect what I need and take my time, maybe get the machining done during winter, when the shops might be slow enough to cut me a deal, lol.

 

[devdg]

most machine shops are busy during the winter for that same thought pattern, they typically are slowest in the summer months as the requests for machining blocks and cranks lower when people would rather drive or ride then fix.

Glad to see you have a plan hope all works out and you can get riding soon

 

[tgwood58]

Hi! guys I'll do an intro in another post.

I my be a bit late on this one but heres my 2 cents anyway, Engine vibration can be caused by a slack timing chain(engine nock/rattle), it doesent have to be all that slack to throw the cam timing out but it will shake the bike to pieces, check your chain tentioner has not backed out? does this engine have a balance shaft?

 

[Lou Ranger]

According to the lubrication diagram, there is a balance shaft - #3:

 

[Flexeril]

sub for research

 

[Lou Ranger]

I'm curious. Does the timing chain actually skip a tooth to cause the vibration or is the increase in slack enough to cause a vibration?

Does the timing chain drive the balance shaft? It would certainly shake things if that were the case, a tooth were jumped and the balance shaft was out of phase.

 

[devdg]

A loose timing chain will cause your valves to open and close at the wrong derees in the crankshaft rotation and may cause your pistons to hit the valves or cause excessive fuel knock. Typically this would also cause poor starts and next to no performance from the engine, in a v8 you might not notice it until you floor it but in a two cylinder you would at idle.

 

[CrazyCabbie]

Well, the bad news is the parts engine was a dud.
The good news is I know the sound of an XS400 DOHC knock...

The original is back in, along with a non-holey header...

Well it still hasn't blown up... And hadn't had the actual knock since one of the first starts this spring.
I can tell that it's getting harder to shift, especially when hot, so trans bearings are probably one source of vibration. At least they're standard bearings... May not even do the babbits this fall/winter...

The cam chain tensioner was sticking, and once it was freed up and reinserted the engine became much quieter when cold, but the valve clatter is HORRIBLE when it warms up. Sounds like the valves are 'farting' at highway speed, lol. It was running really lean, i'm assuming from the valves hardly opening (in time at least). Temporarily fixed that by pinching off my air intake, and the vibration all but disappeared below 3000rpm...

Now I'm waiting for the hot water to be fixed (2 weeks now) before I salvage and swap all the valve train components i need from the spare motor...

 

[Scorpio1963]

Engine bearings might be able to recoated as mentioned sprayed with white metal but if they have been flatten from knocking then they are toast.If you catch a knock quickly you maybe able to save your crank but if not it will scoured also and need to be reground.