Quick/cheap power mods when the head is off?

[somesuch]

Hi all! I noticed a set of nice large washers and a nice large dowell pin in a plastic bag that came with my XS1100 from the previous owner. The washers looked like the ones that go under the valve springs, and the dowel looked like it belonged between the head and the block....seeing no reason why anyone would replace just one nice dowell and all new valve spring washers I assumed that they were just the leftover pieces from when the PO put the head on. I got the bike not runnig, but was told that the valve seals have been done and that the only thing left was to adjust the valves, put the carbs on, and that was it before the bike would run..... I had my doubts, and pulled the head off. Sure enough those parts were missing in my motor, on top of that the valve seals were ready to slide off, head gasket center section was in the cam chain well, and 3 inside head nuts were loose!

Anyway, now that I am here are there any cheap/fast and proven mods that I could do? The bike is a 1979 SG. Should I try to get a later head from Ebay, and use my cams? Big bore? Replace just the rings with filed .25 over in a stock bore? (the bores look perfect and the bike has very few miles) Quick port job? shave the head? Ceramic coat the combustion chambers/exhaust ports ?


Please throw ideas at what are the possibilities. Also, would anyone know where would be a good place to get the replacement rings? I understand that stock size is impossible to find.

Last XS I had in 1997 (the last time I was active on this list I think ) there was definite lack power....and now is my chance!


thank you all in advance

--Nick

[prometheus578]

I don't do power modifications....

My only input is to tell you to toss the center gasket from the cam cavity away. Yamaha did away with that design, and new gaskets sets, (as well as aftermarket) have a redesigned head gasket pattern that doesn't use it.

[79XS11F]

I would just clean it all up real good and make sure all the parts are where they are suppose to be. Make sure everything moves and works smoothly without any binding. If it was a sloppy rebuild he may have even mixed up the part locations so I would go easy on it once it's rebuilt to kind of break it in again.
Rob

[TopCatGr58]

Hey Nick,

Regrettably "cheap" and "power" are not complimentary!

Also, you might want to check your VIN# to ensure your model type, surprised that 79SF didn't catch it, you stated it's a 79SG?

IF the PO put it that far together, with the cam chain installed, then there's always the chance he rotated the engine, and cams possibly not aligned properly? I would ensure that the valves are not bent, check and relap them=cheap supplies for that job! Valve seals are pricey bought alone thru OEM ~ $8.00ea, so for the price of a set, you can get a complete gasket set including seals, new head gasket for a few bucks more!?

Cylinder walls can "look" good...smooth, no scoring, but be badly out of round, spec!? You should have them mic'd to determine the amount of wear. THEN, if in spec, hone and use the 1st oversize rings.

Here's the part numbers from the Yamaha Fich site:
2H7-11610-12-00 or 3J2-11610-10-00
Bike bandit states:
PISTON RINGSET 1ST
(ALTERNATE PARTS) 35277-001 $55.33

Zanottimotor.com sells them for $35.64 a set, but again doesn't state what IS a set, see below?

HOWEVER, they are not clear on "WHAT" constitutes a "SET"?
Are the 2 compression and 3 part oil rings for 1 piston a SET,
or are they stating enough rings for all 4 pistons a SET?

IF a set is only for 1 piston, depending on where you get them, you'll spend between ~$1.50 to >$200.00, just for the rings!
You're close to half the cost of a Big Bore Kit, minus the cost for reboring, BUT if the cylinders are out of spec, then it would need reboring anyways!

There was a recent thread about whether the big bore is worth it for the performance boost! General consensus is/was that IF the engine is still in good condition, not burning oil, or low compression/worn rings, then the cost to benefit is minimal, only about 5-10 hp boost over stock! BUT if the engine is fairly worn, then it's about the only option you have anyways, since the STOCK OS pistons aren't available even though the OS rings ARE available!

Port jobs aren't really needed without the appropriate over the top changes to the rest of the engine to take benefit of the increased flow, larger capacity carbs, modded cams, valve springs, etc., etc.!

IF your head is damaged, then the later model heads with larger valves "MAY" be a slight benefit, but again, don't throw good money away IF your 79 head is still in good shape!
T.C.

[rover]

A 79 is either an F or SF. SG designates a 1980 Special, unless it was sold new in a state that will title it the year it was sold. The 80's had larger valves in the heads, but milder cams. If you have an 80 with the larger valves, use 78-79 cams for a bit of power increase. Some have milled a bit off the head mating surface, but I think that will cause more problems, like valve to piston clearance. Also, you cn clean all the rough edges from the intake/exhaust passages in the head. Do a search for head porting and see what you come up with. And let us know what mods you did, and if they really made more power. Also, you can tell an 80 by the lack of vent hoses on the carbs.

[trbig]

You mean it's not a normal thing to have a bag full of nuts and bolts after a rebuild?!? Maybe THAT is my problem!

The only thing I'd do while I had the head off, is to make sure the valves seal. Tip the head up on a side and pour some gas in each port. Wait a bit and see if you have anything running out past the valves. A tiny amount of seepage may not be a huge concern, but if it runs out.... Flip over and do the other side.

As far as making more HP, for a small bump, you could do a re-hone the cylinders with new rings to bump the compression. A big bore will be considerably more expensive but will gain a few more that way. The 78/79 motors seem to benefit from these more than the later years due to an improved increase in compression due to the smaller head space versus the later heads. This isn't even bringing carburetors into the issue.... or turbos... or NOS.

It all comes down to the old adage... How fast you want to go is directly correlated into how much money you want to throw at it. BUT... if you are looking for 'Bussa performance out of a 29 year old bike... it ain't gonna happen. If you are disappointed with the stock performance of an XS that's running correctly, I don't know of anything really that you can do to make significant enough improvements to impress you.

Tod


P.S. Man, the things that happen when a guy types slow... I started this before TC and Rover.. lol.

[pggg]

If the head's still off, a quick/cheap 'power' mod - trim the intake port entrances to perfectly match the carb manifolds, it'll smooth /improve the flow, there's usually a slight mis-match there on the stock setup. Use a small grinding stone in either a dremel, drill, or best of all a die-grinder

[trbig]

It's been said to NOT smooth up the intake ports much. The rough casting in the ports atomizes the fuel better. I've seen where you actually LOSE HP by porting wrong, so be careful.


Tod

[trbig]

#@$^&%*!!!!!!

[trbig]

Triple Post!!! Grrrrr... Sorry folks.

Seems I would have something really important to say huh?? lol

Tod

[pggg]

yeah don't bother polishing intake ports, just match them to the manifolds but a full port job adds a noticeable kick if done properly

[prometheus578]

"TRBIG stutters" (or is it stammers?)

Seems I would have something really important to say huh

You've been on this site for two years, TRBIG, and we're still waiting!

[trbig]

Pro... could you PLEASE hold your breath and wait for that to happen?


Tod

[somesuch]

Re: I don't do power modifications....

Originally posted by prometheus578
My only input is to tell you to toss the center gasket from the cam cavity away. Yamaha did away with that design, and new gaskets sets, (as well as aftermarket) have a redesigned head gasket pattern that doesn't use it.

will do... thank you. You saved me a lot of time trying to figure out how come my Vesrah gasket does not have the same center design!
--Nick

[somesuch]

Thank you TC for all this info. Sorry it took so long to reply. Everything in this motor looks to be in perfect shape. The valves have not leaked WD40 for two days now and the cylinders/pistons look like new.....literally. I may mike them anyway, but my guess is they are perfect. This bike came from a friend of the original owner who stored it for the past 19 years....never having finished the big bore job he wanted to do.


I will most likely just put the motor together in stock form, and just replace the valve seals, match the intake boots to the ports, and possibly replace the rings with .25 over in a stock (honed) bore. I used .25 over rings in an 82 CB900F with just a hone of the stock bores once and it worked out great. The bike did not burn any oil, and lasted at least 15Kmi more after I had sold it when I saw it back on Craig's list. The guy said that he did not have any problems and just rode the bike for all these miles.

I have seen XS11 heads go for real cheap on Ebay, and maybe one day I'll get one of the later, bigger valve, heads and port it...but that is one day in the future together with the big bore job!


Can't wait to ride it, but will probably be at least two more weeks.

thank you again

--Nick

Originally posted by TopCatGr58
Hey Nick,

Regrettably "cheap" and "power" are not complimentary!

Also, you might want to check your VIN# to ensure your model type, surprised that 79SF didn't catch it, you stated it's a 79SG?

IF the PO put it that far together, with the cam chain installed, then there's always the chance he rotated the engine, and cams possibly not aligned properly? I would ensure that the valves are not bent, check and relap them=cheap supplies for that job! Valve seals are pricey bought alone thru OEM ~ $8.00ea, so for the price of a set, you can get a complete gasket set including seals, new head gasket for a few bucks more!?

Cylinder walls can "look" good...smooth, no scoring, but be badly out of round, spec!? You should have them mic'd to determine the amount of wear. THEN, if in spec, hone and use the 1st oversize rings.

Here's the part numbers from the Yamaha Fich site:
2H7-11610-12-00 or 3J2-11610-10-00
Bike bandit states:
PISTON RINGSET 1ST
(ALTERNATE PARTS) 35277-001 $55.33

Zanottimotor.com sells them for $35.64 a set, but again doesn't state what IS a set, see below?

HOWEVER, they are not clear on "WHAT" constitutes a "SET"?
Are the 2 compression and 3 part oil rings for 1 piston a SET,
or are they stating enough rings for all 4 pistons a SET?

IF a set is only for 1 piston, depending on where you get them, you'll spend between ~$1.50 to >$200.00, just for the rings!
You're close to half the cost of a Big Bore Kit, minus the cost for reboring, BUT if the cylinders are out of spec, then it would need reboring anyways!

There was a recent thread about whether the big bore is worth it for the performance boost! General consensus is/was that IF the engine is still in good condition, not burning oil, or low compression/worn rings, then the cost to benefit is minimal, only about 5-10 hp boost over stock! BUT if the engine is fairly worn, then it's about the only option you have anyways, since the STOCK OS pistons aren't available even though the OS rings ARE available!

Port jobs aren't really needed without the appropriate over the top changes to the rest of the engine to take benefit of the increased flow, larger capacity carbs, modded cams, valve springs, etc., etc.!

IF your head is damaged, then the later model heads with larger valves "MAY" be a slight benefit, but again, don't throw good money away IF your 79 head is still in good shape!
T.C.