Big Bore Kit

[Shuriken]

I'm just curious how the big bore kit has affected us all and if anyone overall is unhappy with the price/value/performance ratio it provides.....

Ben

[strom]

My oil rings and stuff crapped out on me.
Need the kit, don't have no dough.

LP

[Shuriken]

I had my grubby's on the kit once last summer. I was going to do the install but ran so low on cash I had to resell it. I hope that's not the last time I'll have one because I want to rebuild the head and do the kit and ... perhaps a complete restore down the road a bit. This is all of course if I don't go plunking down hard cash on an FZ1..........

What would be a reasonable estimate for a complete big bore kit install and complete cylinder head repair? $1000?

Ben

[TopCatGr58]

Hey there Ben,

Well, from what I've heard/seen, the kits can be gotten for around $400, which includes the head gasket, the most expensive one, the rest you can actually make yourself. I would recommend replacing the valve seals while you're in there, rubber only lasts so long!? That's another $60 or so for a set of 8. My local machine shop charged $40 a hole for the boring, another $160 plus taxes. I reconditioned my valves and seats myself, less than $10.00 for the tool and grinding/lapping compound. Dependent upon the condition of your valves and whether you may need to replace any, Yamaha wants over $35.00 each, but I've seen folks talk about getting them elsewhere for at least half that!!! And since you've got to tear the top end off, you might need to replace your cam chain. And how's your clutch?? Another $100 for new friction discs and springs again depending upon brand and purchase place!? So...you could end up spending $1k, or you might be able to get it done for less, but looks like $750 would be a more realistic figure, IMHO. You'll need a low scale/range torque wrench, for those cam sprockets bolts and bearing cap nuts, head nuts that require only 10, 7, 25 ft/lbs respectively, standard wrenches start at 10...not very accurate for these delicate/precise requirements.

I'm very happy with mine, cylinders were badly rusted, couldn't get any standard oversized pistons from Yamaha, went with the smaller 1179 to keep the cylinder sleeve walls as thick as possible! Good Luck. T.C.

[sixtysix]

Still sitting in the box......maybe this winter

[Shuriken]

I already have a set of valve seals - got them for a real hot deal. I also have the tools and several torque wrenches. I really can't imagine the valves being that good, especially with my low compression. I don't have any idea if the cam chains are still available or not, I've never looked for the XS11 chain in particular. I have two XS11's with probably identical mileage. Perhaps the parts bike has a decent head, I haven't had time to pull it and look. It's a 78 and my bike is an 80. I've heard the swap should be okay.

I'd sure like to ride someone's big bore bike to see what the comparison is like to stock.... For instance, comparisons between the stock and big bore bikes with identical setups at the same elevation and same carb settings (possible? ;-P)

Ben

[Snow]

partsnmore has the cam chains for about $32. My bike has the 1196 kit in it and it runs like crap due to carb problems that I'm still sorting out

[Shuriken]

It seems you have to dial in the big bore kit like you do the carbs!

I want to ride a big bore setup running hyper and compare it to V-Max, or see dynos from both.

Has anyone dyno'd their big bore setup?

Ben

[ElCid]

A couple of years ago, I had a header mounting bolt break off in the head of my 79 special. I couldn't get it out without pulling the motor and didn't have the skills or equipment for that big a job so I took it to my local drag shop (Performance Cycle Works in Schenectady, NY). I figured most of the money I would spend would be in labor so I decided now would be a good time to do all the upgrades I had been dreaming about.

So, I took my zero perecent credit card and had a Wiseco 1179 piston kit installed. While they were at it, they worked their magic on the ports and valve seats and put on a Jardine 4-into-one.

The first few times I rode it, it scared the hell out of me. It revs very quickly and gets going very fast in a short period time. The first time I tried to launch it the way I would have prior to the rebuild, the tire smoked heavily and when it hooked up the front end came way up.

Even now, after a couple of seasons riding it, a tweak of the throttle still leaves me grinning ear to ear and saying "man that's fast".

Needless to say, I'm very pleased. And the best part? If I ever get to the end of its ability to surprise me, the bigger kit's out there waiting.

[Shuriken]

EICid,

Thanks for the info. I just took my XS out today for the first time in probably 3 months. Had a flat tire and gas cap problem, and have been really busy.

It wouldn't start for anything. I drained all the fuel and it looked like there was a lot of water in it. I then installed new spark plugs and it fired up. I got on it immediately and forgot how fast even this old beat up bike of mine gets up. I realized I was doing 75 in town and slowed down.

I can't wait for the rebuild on mine. That is if I don't see some sort of other smoking deal on a V-Max, V-65, or FZ1.

I'm willing to bet one reason your XS gets up so madly is because of the valve and port work. If the timing is right, the valve clearances are correct, good flow, big bore.... this thing should smack out at least 100hp at the crank.

Plus you probably live at a decent elevation where your bike can breathe. I'm at 6,700.



Ben

[dragxs11]

Ben,

I'll be big boring this winter and port & polishing the head. I will then dyno the bike after a gentle break-in. There is no maybe here.... it will happen. I will, of course, post the results with a full list of performance mods.

Matt

[Shuriken]

I can't wait. Even better that it's not a maybe. ;-)

Ben

[Mike Hart]

mototuneusa break-in "secrets"

Not TOO gentle now...

check this out...
http://www.mototuneusa.com/break_in_secrets.htm


This guy is also a porting fanatic, and mostly says SMALLER is better! It being all about port velocity... interesting stuff.

[dragxs11]

Huh,
That was quite interesting Mike, thanks for posting that. When the time comes I'll have to look into that further.
Yeah Ben, I know that sounds kinda funny, but I wanted to get the point across that for me, my bike is serious business. I'm deturmined to get it where I want it.

[Shuriken]

I have to agree Mike, great link and food for thought. I hadn't thought about port velocity. After reading the article, it makes sense to me.

I suppose there are limits to everything. If you get it too small the flow rate might be so pathetically reduced as to have negative effects, in contrast with too large creating far too little of vacuum.

JB weld on the intake ports? Amazing stuff if it holds up and doesn't rattle loose with disastrous damage. That article and his performance results seem to back up his claims.

To me it seems that reducing port size has a similar effect as a turbo. With turbo systems the engine can be forcefed or pumped extra air. If reduced port size does indeed increase velocity (venturi effect... carbs... ??) then it is related to what turbos do.

I'd be willing to try the mod when I did the big bore kit but I wouldn't know how small to make the ports and other things.

These da*n bikes are breaking me. I want to read the book on muffler design and all of this porting and big bore stuff is driving me nuts. So much one can learn, so many untested horsepower, so few wheelies...... Just not enough cash to burn.

Ben