Throttle Shaft Seals

On the Mikunis, yes. On the Hitachis, no. A good-fitting screwdriver should do the trick. Probably a good idea to use a scratch awl to mark the back of the butterflies where they meet the shaft so you can be sure you reinstall them in the same position they came out.

Oh, and I did make reference to the peened butterfly screws in the Mikuni Carb Cleaning file.

 

$90 for the seals??? On a Maxim??? You NEED to get in touch with Chacal... his prices are MUCH lower than that.
And I'm all for you getting the right parts in there, reconditioning your old parts is just wizzing on a forest fire. You aren't buying much for the effort.

 

Chacal's price for seals is $32.00, and they're in stock (I just ordered mine last week). A big blob of vaseline on the seals will last for an afternoon as a temporary fix, but goops up your butterflies in very short order, although it provides a very graphic demonstration of which ones leak. Pretty tough to get enough on the inside seals to make it work too.

 

Parts are from Chacal... but note I said the Seal Kit (aka all the parts needed to be replaced when splitting the rack).

I really only want to do it once so the outer two are the only seals I can change without all the parts listed below...

seals: HCP38BSET8 $32.95
Screws: HCP1347SET8 $5.00
Shims: HCP3991SET8 $14.95
Screwdriver: HCP5901 $14.95 (JIS for the Butterflys)
E-clips: HCP2909SET2 $3.00 x 4
O-rings: HCP92SET6 $7.50 (Fuel Rail)
7.50 shipping

= $87.35

And chacal is the only person who has them regardless. I work for Yamaha and they don't split up the throttle shaft or butteryfly's in the fiche... So Chacal is the only place to get the Throttle Shaft parts from.

So I (and we all) should truly thank him as otherwise when these seals leak we would all be pretty screwed...

Cheers
Dave

 

Awesome, Thanks

Dave

 

Azrael be sure when you do put them back together you use thread locker on those butterfly screws.

 

That I will do.

So, I noticed today that she will hang when I pull to a stop, but if I give the throttle a good hard blip it will rev up but then drop down to a stalling idle... however if I turn the idle screw in more the bike actually starts to run away from me when I am coming to a stop 8O

Any input from the wiz's out there or is that still an atribute of the shaft seals? Any other input about other issues to look for before tearing the rack apart?

Cheers
Dave

 

All clamps tight on th mounts, carbs aligned in th mounts no cracked rubbers
or it's just time to bite th bullet and break th rack 'n do those damn seals. Synch' and adjust. They'll be good for a long time afterwards.

 

Well it looks like my troubles run much deeper than I thought... I had it in the shop so I decided to do a leak down as one of the other techs had a new tester from snap-on was dying to try it. Turns out cyls 1,2,4 have only a 2-4% pressure loss, but my number 3 cyl has a 60% loss and such is burning oil aka running rich... I knew she was burning oil but I figured it was just a little wear on all cys vs one really bad one... So I would assume it is a big factor in my running issue and will start on the repairs.

So I guess for now I will order a set of rings for cyl 3 along with a base/head gasket and adjust the valves after rebuilding.
Do you all think I should change the valve guide seals while in there?
and maybe lap the valves?

Kinda peeved but I guess that's how it goes sometimes...

Cheers
Dave

 

Don't put new rings in only one cylinder; and don't order rings at all until you've pulled it down and inspected and measured the bores. Otherwise don't bother.

By all means lap the valves and install new valve stem seals while the head is off.

Be careful of the valve spring coil orientation upon reassembly, it's important.

All that being said, have you done a compression test? Or are you basing your decision to do all of this expensive engine work on one leak-down test?

 

I have only done a leak down.
My understanding is that a compression test is essentially pointless if you have done a leak down seeing as compression tells you if you are losing pressure, where as a leak down tells you both if you are and where you are losing it. I could hear the wooshing coming out of the crank so my rings are bad. Running 100PSI on the test.

Open to any input though

Cheers
Dave

 

sort of, maybe but the regular compression test may tell you that the compression is fine and the leak down says it leaks at the rings when it leaks, it's got to leak somewhere

 

I'm inclined to agree with needing the compression test. You need to know if the cylinder is pumping volume. The leakdown could be in error (I've seen and done this so don't assume it is right the first time out). Use the compression figures to back up the leak-down test. It could well be a hung valve, or carbon on a valve face... Were you able to listen to where the air was going with the leak-down? You should hear the sound of escaping air either at the intake, the exhaust or the crankcase servicing port.

 

Ok, I will run a compression test then.

Yeah, it was coming out of the crankcase. Could hear it through the oil fill port.

 

So it turns out there is nowhere in the city I can rent a compression tester. So I guess I will see if I can borrow one from work tomorrow :roll:

Dave

 

Go to your nearest Canadian Tire and buy one for probably about $25.

Or "Google" "auto parts Vancouver, BC" like I just did, find your nearest NAPA and buy one (probably for about $25.)

Sears? It's a good addition to your toolbox. I have one that I've had for about 40 years now and one I bought a couple of years ago just to get the 12mm plug adapter in the kit.

 

So I got results of a compession test today.

4 3 2 1
180 140 170 175

(note: coldish engine, throttle closed)

and the leak down prove it is the rings so I guess I gotta look into tearing her down...

 

NO no no no...the throttle MUST be held open (carbs off is ok too). Engine temp is not a concern.
The result is skewed but in general you are right, #3 isn't as happy as the other three. Try running it for a week and try the compression test again to see if the numbers improve.

 

Ok, Did a comp test again today, WOT for all the tests

4 3 2 1
185 170 180 190

:?

I know I am leaking oil into cyl 3 so I ran the bike for a few seconds as I figured some unburnt oil/fuel may have sealed the rings. Then tested cyl 4 again and still got 165

I am confused to how it can fluctuate so much by opening the throttle...

Any input would be appreciated

Cheers
Dave

 

Based upon your initial leakdown and the subsequent compression tests, you do have a ring issue but I would not classify it as terminal. If you are not having any other issues, I'd just run it, the WOT compression is close enough that I wouldn't be concerned. Just check the numbers again in a week or two and see if they haven't improved. It may well be that the rings might, just might seal a little better with excersize but it is more likely that nothing will change. You can spend the interim time until it NEEDS the rebuild saving up for the new parts. And stock rings are NOT cheap.