Over size pistons needed

[teck_mountain]

Okay

Seems my cylinders are shaped like a funnel and I need to install over sized pistons. However, I'm told Yamaha does not make them any more. Any ideas?

1979 xs 100 special

[ratbyk]

O/S Pistons

Wiesco big bore kit's are still available. Never done it yet myself.
There is a huge long thread on it. Supposed to come with pistons,rings, pins and big bore head gasket. Cost is in the $550.00 range. Wiesco should have a web site. Why don't you goggle it and check out.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[Huron52]

I hope this works...

http://www.wiseco.com/PDFcatalogs/ps04-yamaha.pdf

It is a PDF file but it should open if not delete some of the address and try again...

Good Luck

[Huron52]

Oh and yes you should have adobe reader to see it. They are manufactured in Ontario but your local dealer should be able to get them for you. You may have to supply him with the part numbers.

[Snow]

I've heard that rumor too Got mine for a reasonable price from Pro-Flo of Pensacola Florida in the US. I think it was cheaper than Wiseco's list price, even including shipping. Same price for either size kit.

Includes everything you need except tools, labor, and the machining...and of course experience, but you get the along the way

[TopCatGr58]

Here's a copy from their web page along with the link:

XS1100, 4 Cyl. 1179cc 78mm - 55.85mm
10.25:1
W-K1179
$365.95

**The 78mm I believe is a typo, that kit uses 74mm diam!

Kit includes, 4 Pistons, Ring Sets, Wrist Pins, Circlips and 1 Graphite Head Gasket 1196cc 78mm - 55.85mm

10.25:1
W-K1196
$365.95

Pro-Flo in Fla. kits web page

HTH, a happy Big Bore user!!

[teck_mountain]

big bore

Well, I'm going to use a big bore kit. Thanks for all the help. I was wondering,...will this increase the overall power of the bike?

[ratbyk]

Power Increase

The big-bore kit will increase power in three ways.

1. Fresh pistons and rings will increase compression and combustion pressures.= More power.

2.The big bore pistons I believe have a compression ratio of 10.25 to 1. = More power. (quite a bit by the way.)

3. Your engine displacement is bigger. = More power.

You will likely have to use high test fuel but that cost increase will be offset with better fuel economy. Unless you start to be throttle happy. Then fuel mileage will be the same or a little less. The higher compression will develop more power out of each drop of fuel. It will create more BTU's for each drop of fuel.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[pgg]

1196 kit gives more 'urge'. Felt at low and midrange. Great for touring. Not much top end boost on its own. A few engine tweaks needed to tap the kits' potential. Still good on it's own though.

[John]

What is the smallest kit available? I am contemplating doing it to one of my spare engines, but I don't want to do anything too radical that will require to much modification to other systems. I already have a Jardine 4-2 header, and am running the carbs from the Organ Donor, so they can be tweeked, but I don't want to get too radical.
But on the other hand, there is this FJ1100 (swmbo's) in my garage that I would like to beat just once!

[TopCatGr58]

Hey there John,

The 1179cc kit is the smallest one, however it is still a whopping 74mm diameter vs. the 71.5 stock and still bigger than the max Yamaha recommended allowed stock overbore of 72.5! I'm running stock cams, carbs with 3 sizes larger jets due to Indy Filters and 4-1 pipes, but that's about all the tweaking I've done, and it runs great, plenty of power and topend, possibly a little loss of low end grunt due to the 4-1's, but I don't like to run it like a Harley!!

And this will allow you room for another boring up to the 1196 if these ever fail!!!! It does run a little warmer with the thinner cylinder sleeves(stock) but after richening up the ratio, it's okay. Just try not to get stuck in any severe stop and go traffic in the middle of summer with 95+temps.....the smell of burning oil from the heads isn't a pleasant one!!!! BTDT!!

[dragxs11]

Thanks T.C. You just saved me about $175. I'm ordering my kit tomorrow.
Matt

[mitch]

Beat the wife

Hey John , sneak out and unplug one of the FJ,s plug wires cause thats the only way Your gonna beat her!! ........MITCH