Big bore kits

[motoman]

Try Kroil from Amazon....supposed to dissolve rust crystals.


John

Yep it do........and FWIW you can buy it at your local Ace or Tru-Valu Hardware store.

[natemoen]

Well it is 1174 and 1196 so there is almost nothing in difference in the sizes. It is only 5.5 cc's per cylinder.

[crazy steve]

1. My question again concerns the big bore kits. How much honing would be done to accomodate an 1196 verses say 1147. If I find the sleeves are pitted would the honing for the larger kit take off enough to negate the pitting is where I'm going with this.
2. Are these kits all high compression racing type kits. If so, what other considerations must be accounted for after instalation? IE tuning, shaft upgrade, starter upgrade, battery cranking amps etc.

I believe the kit sizes are actually 1179 and 1196, so either will be big enough to remove all but the very worst pitting. I don't think the 1179 kit is out there anymore though, so this may be moot. The disadvantage to the larger kit is your cylinder liners are that much thinner, and bore size stability is poorer. You may see slightly increased oil consumption over a stock bore in any case.

In terms of the compression increase, you'll see several effects. The first will be the motor will run hotter, both from the compression bump and the bore increase. A jet size increase will definitely be called for, you might even try a one step colder plug. You'll want to run only premium fuel, and increasing initial timing may be called for. You may want to look at an oil cooler, but I'd check oil temps before I spent that money. A lot of this will depend on how 'hot' you tune the motor and what you run for intake/exhaust. One thing I would seriously consider is using the '80-81 head with it's larger valves with the early longer-duration cams.

The only comment I'll make on the shaft drive is I would hesitate to use a 750/850 FD if you're making more power as these seem to be barely capable for the stock power.

Yes, the starter will see increased stress, but other than having an expensive rewind done, the best solution IMO here would be to install larger cables for the battery and starter and eliminate the 'through-the-frame' ground paths between the negative battery terminal and the motor. I'm not aware of a 'heavy duty' starter for these. None of this may even be needed, again I'd wait to see. A good-quality OEM-sized battery should be fine. To tell the truth, you're only talking a 8% displacement increase here and the Harleys I see that are punched out don't start having starter problems until the increases get above 25% or more.

[TomB]

The other way of looking at it is, does the kit you are planning to use actually increase the compression??

Check out the pin to piston crown heights, if they're the same as the pistons you have you shouldn't have a problem with having to uprate your starter. The only thing on that is ....if you had really low compression before because the pistons/bore were worn badly, and your starter/battery coped good it may not once you have a fresh engine with standard compression, not because your new big bore kit has a higher compression design, simply because its in factory standard compression.

That said, if you do end up with a higher piston crown therefore higher compression design, you can lower the compression with thicker head gaskets (I did this on '66 500 Triumph to get down to 8:1 from 9:1 pistons I had), or a compression lowering plate under your barrels like Turbo bikes use.

As Steve says, higher compression isn't just something to worry about with the starter motor and battery, ignition detonation is an issue. Any none standard mods should be looked at as if none of your ignition/carburation set-up are correct, doing a full throttle range of plug chops is a minimum. Some rolling road diagnostic time is nice but costs (which is why I'm good at plug chops now ....coz I'm a cheap-ass)

On the bore size and cleaning up of erosion marks? Yamaha 4th oversize pistons are still occasionally around NOS (if you hunt them out) and will take the bore out to 1133, I've seen really bad scoring that has been easily taken out by going out 0.040"


.

[trbig]

The other way of looking at it is, does the kit you are planning to use actually increase the compression??

The aftermarket kits seem to have a piston crown that's in between the stock pistons. Meaning: Slightly more crowned than the stock 78-79 nearly flat pistons, and slightly less crowned than the later 80+ pistons. Since Wiseco approved that design for all years, and all the aftermarket pistons I've seen match Wiseco, I wouldn't worry about any valve to piston contact. I've got a couple pics of that somewhere..

The only comment I'll make on the shaft drive is I would hesitate to use a 750/850 FD if you're making more power as these seem to be barely capable for the stock power.

Granted, I tore up one of the earlier type 1 750 final drives, the type 2 that all the 850's had will hold up to anything you throw at it. I've got the 1179 kit in mine (Never had to run anything but regular unleaded) and have abused and punished this final drive worse than anyone I've heard of with the amount of starting launches and hundreds of wheelies. Many of the engine drive parts that were designed for the 1100 have been destroyed while the final drive still performs flawlessly. I'm only estimating since I've changed gauges out a few times, but with an average of @ 25k miles a year, and with all the abuse I've dealt it, the 850 final drive still has barely any fine shavings at all attached to the magnetic plug at changes, and doesn't make any noise, build heat, or have excessive slop after at least 75-100k miles. I'm sure it has helped only running 100% synthetic lube in it and changing it at least once a year, but I would not have any misgivings about the ability of it to hold up to any kind of power the 1100 can make under normal aspiration. Just my 2 cents.

[trbig]

Found those pics...


Here is the difference between the early and late model piston crowns. 78-79 piston on right, 80+ on the left.









And this is a Wiseco piston compared to a later 80+ piston. Kind of hard to see here, but there's less crown to the Wiseco. What does this mean? If all things were equal and you compared the aftermarket pistons vs NEW stock OEM pistons, you should get a bump in compression over the earlier model pistons and a slight decrease over the later pistons. BUT... you are probably rebuilding a tired motor, so either one you're rebuilding is going to help immensely. What I did find a bit disappointing is there was no real seat of the pants feel of more HP being made after the big bore. All it really does is freshen up the motor, so if you're doing it simply for the HP boost, I've a feeling you'll be disappointed.

[crazy steve]

You'll get a compression increase from just the overbore, all else being equal. You've got 23.5cc more swept volume per cylinder (assuming a 1196 kit), being compressed into the same combustion chamber. That's a 8.5% increase, look for about the same jump in compression, with some 'windage' for the slightly different piston crown. Figure it's between 9.6 and nearly 10:1...

Tod, with your later motor and smaller bore, you're only seeing about a 9.6:1 ratio at most. I'd personally consider that the upper limit for running regular fuel with no issues. Get close to 10:1, and regular will make the motor unhappy....

[mack]

Thanx

for the input. After considering everything I'm putting it off for now. I will spend some time investigating the jugs I have, to see if I can get away with a light honing. I'd hate to have to run high test in it up here. Regular gas is already about $5.00 gallon at times. For the E, I have a spare motor I can use. It has just about the same milage on it so saving the original jugs is not an emergency.

[crazy steve]

Mack, you can detune a high-compression motor for lower-octane fuel, but they generally don't like it. You have to retard the timing, and it doesn't do anything for the low end that you'll like....

[Rasputin]

o here are some pics (again) of some Russ Collins Engineering pistons I have. What would be the general consensus of the compression you would have with these?
I have put little or rather NO effort as of yet to find the coreect ring I am missing, but they are in great shape so I should look to see.









They say they are 74mm up inside the piston itself.

[crazy steve]

o here are some pics (again) of some Russ Collins Engineering pistons I have. What would be the general consensus of the compression you would have with these?
I have put little or rather NO effort as of yet to find the coreect ring I am missing, but they are in great shape so I should look to see.



They say they are 74mm up inside the piston itself.

Whoa baby, those are some big 'uns! I'd bet those are 12.5:1 at least, maybe more. Race gas or alcohol.....

Probably want to check piston-to-head clearance with those!

[Rasputin]

Whoa baby, those are some big 'uns! I'd bet those are 12.5:1 at least, maybe more. Race gas or alcohol.....

Probably want to check piston-to-head clearance with those!

Just wondering if you happened to note the "Button" type wrist pins?