1977 Yamaha XS750D

Found some small vac leaks in the carbs. I replaced the seals once already but something prevented them from being permanant. So I went ahead and did it again and I also found two pilot screws that decided to break off. fixed and replaced those. Went down on my main jets to 132.5 I was at a 137.5, not sure why. But it's all fixed and runs so much smoother.

Except for the noisy vavles... I'll tear the cover off again tomorrow and inspect the valve clearances I kind of hope they are out of spec so I can just get the correct shims in and be done with it. because if they're good then the cams might be bad or a spring is broken. and that'll require more money and more time.

On a side note before the vavles decided to get noisy I ripped the bike down the street hitting 9k RPM. At that point though I'm passed the powerband and just winding gears. I'll probably shift around 7.5 or 8k
I need a datalogger hahah I should probably fine tune the carbs, and get a seat upholstered, and finish my gauge install
 
Exhaust cam is shot! each lobe is flat.

I'm thinking that with the regrind they went through the hardened layer. Bike mechanic buddy of mine told me that's the most likely scenario.
 
I called them and they told me to ship it back to them and they'll check the cam hardness compared the the shim hardness, repair it and send it back. Now if there's a charge for the repair has yet to be determined.
 
Cams came back today, Woo Hoo.

Open the box unwrap the cams...

They're oily but still in the exact same condition I sent them in as. The exhaust cam is flat on all the lobes. I'm just kind of at a loss. I'll call them tomorrow and kind of give them the WTF?

So there's my progress :(
 
You would think they would at least include a write-up of the inspection results or explanation on the cams' condition.....

who did the cams again? I'm feeling like I should steer clear of the company.
 
Delta cams in WA. I just got off the phone with one of the guys and I sent him pictures and he told me that that is how the cam is profiled.

Seems a bit weird to me, but he explained how it was .008" more worn and their welder added material and then they hard faced the lobes. I don't really want to put them back in and see if they are quiet or not, even though he insisted they would be quieter than a tradition pointed lobe would be.

and yes I requested they do a profile of the cams for me to have paperwork but I didn't get that either. sort of mixed reviews on them from me. They did do the rework for free! that's really good on their part, but didn't do the little thing of cam profile so I can actually say my lift is xxxx and stock is xxxx so I have this much more.

Ohh well time to figure out if the machine shop ever shimmed them correctly or not and get that sorted out, then hopefully ride it this weekend
 
Ohh here's the actual lobe
 

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there's two things that need done with a cam modified as such. It needs to be properly degree'd in....this usually means getting an adjustable cam gear or having your's modified to be adjustable to really get the most out of it. Secondly, you def. need to verify they've been shimmed to correct tolerances(after you degree in and set camchain tension). I'd be asking delta cams if they suggest different clearance than stock.

that flat portion is that way for more duration....your valve will be open longer. They are correct in saying the profile is designed that way. If you want to make sure that they are not "worn" you can measure the lobe from point to point and compare it to the manual for what's acceptable stock lobe measurements.

Once you've done all of that, synchronize the rack of carbs...sometimes your ears play tricks on you when the carbs are making small hiccups and strange air noises if they are out of sync. After all of that....if it's still noisy I'd be concerned and get out a stethoscope to try to pinpoint it.
 
I haven't really seen to many cams just a few for SBC and some SBF and the ones for my subaru so I guess I was just a little thrown off. They did explain it to me that it keeps the valve open longer I can completely visualize the valve staying open at it's peak longer this way, just seemed very off to me

Yeah I'm working on the shims right now. All the intakes are within spec, BUT all the exhaust are really loose. I need to go up shims from
270 to 300
270 to 305
265 to 285.

Not too sure why they are so loose on the exhaust cam. I would think the profile they did for me before would be exactly the same as this time. If that's true then my machine shop didn't install the correct shims the first time, and that certainly would explain the noisy valves from before.

As far as degreeing the cam? I'm not sure how to do that on this bike, but if there is an easy method I'm all ears. I was just going to set TDC on the pointer and alight the dots on the cams to the marks on the cam caps like the manual says.

BTW I do have another set of cams that have the adjustable cam gears on them
 
Back together and all shimmed up. Took her for a ride today and she was smoking like a mo-fo, when all warmed up. Got home and checked the oil expecting to see it real low burnt up, and to my surprise it wasn't. I'm wondering if the muffler got a bit oil soaked and is just burning it off as I ride.

I'll take it out tomorrow and give it a few test rides. I know I did a shit job of initially seating the rings so we'll see what happens with more miles.

Also the damn thing completely popped out of second gear at high rpm's, should have sent out 2nd and 5th gear and had them undercut
 
clay69camaro said:
Back together and all shimmed up. Took her for a ride today and she was smoking like a mo-fo, when all warmed up. Got home and checked the oil expecting to see it real low burnt up, and to my surprise it wasn't. I'm wondering if the muffler got a bit oil soaked and is just burning it off as I ride.

I'll take it out tomorrow and give it a few test rides. I know I did a shit job of initially seating the rings so we'll see what happens with more miles.

Also the damn thing completely popped out of second gear at high rpm's, should have sent out 2nd and 5th gear and had them undercut
Click to expand...

have you done the shim swap from the second gear fix writeup?
 
clay69camaro said:
I didn't do the swap, i installed a new gear instead.

Looks like I should have done both :(
Click to expand...

I've done it on 2 of my 5 triples.... one of them wouldn't go into 2nd AT ALL, flipped the shim to the other side of the gear and now it works great and doesn't kick back out. I'm glad it's as simple as it is to do on the triple, poor xs11 guys have to open the cases to do it on theirs.
 
Im in!
About your cam issues, when you fit cams with higher lift you mav have to use beehive springs, have you researced this? And if your cam profile works nicely, and these guys will send you a master profile i am very interested in a copy, as i am considering doing this mod on my build.
 
datadavid said:
Im in!
About your cam issues, when you fit cams with higher lift you mav have to use beehive springs, have you researced this? And if your cam profile works nicely, and these guys will send you a master profile i am very interested in a copy, as i am considering doing this mod on my build.
Click to expand...

I asked them to give me a profile of my cam when they had it last and that didn't work. They are not too good with their communication.


Bike is still smoking and burning oil like crazy. I have to clean my plugs after every ride and it's gone through two quarts of oil in less than 100 miles.

I'm going to have to do a compression and leak down test to find out if it's the rings or the valve seals. Either way it's really annoying because it's all fresh.
 
That's crazy! Maybe you didn't get the valve seals seated correctly? They have to be pushed on firmly. And this is on all three pots?
 
datadavid said:
That's crazy! Maybe you didn't get the valve seals seated correctly? They have to be pushed on firmly. And this is on all three pots?
Click to expand...

Local machine shop did the valve work and installed new seals. I've had them do work on some of my other machines so I have confidence they did it right. and yeah all 3 cylinders have dirty oil burnt up plugs after each ride.

I'll post up my compression results in a bit. I'll have to source a leak down tester, so just a compression test for now
 
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