Hi gents!

Got some good news yesterday from our provincial licencing agency. While the had initially classified the VTR in with the supersports, they have now come around to realize that it is not. In practical terms, this means BIG TIME savings for me both this year and in the coming years as plates for said supersports should hit $1400 by next year (should mention it includes liability insurance).

So, with this freed up money, my mind naturally wanders to things like.... hi-comp pistons!! My question is this: My bike currrently has 60K+ miles on it. It run perfectly well, doesn't smoke or burn oil. In light of the latter, it is reasonable to assume that I could have hi-comp pistons installed with a simple re-honing of the cylinders or is that being overly optimistic? As I am on a semi-limited budget (have an eight month-old daughter...) and have no facility in which to disassemble and rebuild an engine, I could possibly swing the pistons and install if this is all that is needed but a re-bore and the rest would put it out of reach (for at least one year anyhow). Also, what about all the bearings and other wear items? The cam chains were replaced when I had the Yosh cams installed (about 6000 miles ago).

thanks for your responses

cheers

 

Hi Mik,
IMO, no. Assume nothing, check the dimensions of the bores and go from there.

 

Mikstr, if it were me I'd wait till Winter then take it to your wrench/motorhead and have him tear it down and check the bores. You really can't decide what's best till that's done...Otherwise, you could find a spare motor and have him start right away

Once the pro sees the bores he can tell you your options, which could be something like this:

1- In spec, you could get away with a simple hone with a dingleberry and install stock sized hi-comp pistons & rings, new rod & main bearings, gaskets and be outta there for minimal cost with your old motor

2-Outta spec, outta round or tapered too much opens up a new door to bore them out! Not sure how much boring out to do, but I'm sure somebody here has some experience with it. Also, there will be a minimum boring number anyway in order to get them right again if they are outta spec. Then just get matching pistons & rings made custom and you'll then have a bigger bike

 

methinks I`ll wait until next Fall and have it done right....

cheers guys

 

Probably quite a bit of taper at 60k miles.

Buy a low mile used engine and start with that. boring and custom pistons get expensive and you have to buy 4 slugs. Hone it and buy 4 custom pistons that fit and sell the other 2 to somebody with stock bores, at cost.

 

Could he hone a minimal amount and just use stock sized HC pistons and with OS rings? Ron Ayers sell +0.25 & +0.50 rings:
http://fiche.ronayers.com/Index.cfm/...NKSHAFT_PISTON

 

Maybe I missed something, why does he need to buy 4 pistons?

 

I think it's cuz they make them mostly in batches of 4 cuz most bikes have 4 jugs

 

This wont work! I checked and the tolerance is only 0.200mm between bore and piston size, so you'd have to size up both pistons & rings...

 

Ah, so find someone else who wants OS jugs and split the cost!

 

You don't want that much ring hanging out of the piston, you have to upsize the pistons to match.

Check the JE website there is a custom piston order page. I'm pretty sure you could order just 2 pistons.

 

Exactly! I may even be interested in 0.5 over

http://www.jepistons.com/pdf/customp...-orderform.pdf

Anybody know how much power can be had boring 0.5 over?

 

Rick you going to go with the standard ring end gaps or are you going to tighten them up?

Also anyone ever check out realseal rings? Their rings overlap the ends.

 

I have std rings, but haven't check the gaps yet. The specs are:
1st 0.55mm
2nd 0.70mm
oil ring 0.90mm

I've heard of overlaping rings, but are they any better? I figured the usual 120 degree staggering of std rings gave a good compression seal. Does realseal give any kinda guarantee that they seal mo betta?

 

You can lightly hone and install off-the-shelf pistons, but they tend to run small (JE's do anyway..

For a better fit and more honing, you'll wan to size the pistons to fit, which makes them a custom order. We're only talking a couple thaousandths, not enough to need oversize rings. Just tightening up the skirt clearance.

 

That sounds good, but what if you did bore them 0.5mm over, would there be a noticeable gain in power?

 

By my calcs boring 0.5mm over = 1006.27 cm3 or a gain of 10 cc...probably not worth the money if you don't have to do it...

 

Might as well go 2mm, if you're going to do that. something like 30 cc of displacement.

Or you can buy a set of wheels, or lighten the crank and flywheel. It won't show more on the dyno, but it sure does feel like more. Lower inertia has the same effect as more power.

 

I just did the math:
1 mm over gives 1015 cc
2 mm over gives 1036 cc

The problem I could see would be getting rings for those....


Any idea if a piston (100 mm bore) from a RC51 would fit? (deck height, piston pin diameter,...) That would be a nice alternative, as it has a higher compression ratio and you could go with stock rings

 

Good idea! I'd be very interested in wedging in RC51 pistons & rings!

 

At that point you may need custom rods

 

And if I was considerign doing all that work I might also suggest pinning the top of the cylinder bore

 

true or at least custom rod pins...

 

I was refering to the distance from the piston crown to the center of the wrist pin on the RC cylinder may be different than that on the Hawk. I didn't even consider the Dia of the pin.

 

yep, sure to run into a problem there too cuz stroke on RC51 is around 63.5 and SH is 66mm...

 

many variables to consider but it sure would be nice if they could be made to fit without too much trouble. For example, a friend of mine had a built-up Polaris Indy 600 snowmobile engine (triple cylinders) that used older model RM250 pistons (which bumped displacment up to 707 cc if I remember correctly).

 

I just had a look at the Ron Ayers site and the piston pins do not have the same numbers (VTR: 13111-MBB-000, RC: 13111-MCF-000). Also, the clip diameter is listed as 24 mm for the VTR and 23 mm for the RC. Oh well....

 

bump this thread:

with the data below, where the 'hawk bore and stroke are the same as the sv1000 bore and stroke, would that mean in order to get higher compression like the sv1000 in out lacking-in-that-category 'hawk all we would need to do would be swap the pistons? or am I overlooking something like valve clearance. any input guys?

Honda Super Hawk Engine:
Engine Type: 996cc liquid-cooled 90-degree V-twin
Bore and Stroke: 98.0mm x 66.0mm
Compression Ratio: 9.4:1
Valve Train: DOHC; four valves per cylinder
Carburetion: Two 48mm slanted flat-slide CV
Ignition: Computer-controlled digital transistorized with electronic advance

06 Sv1000s engine
Engine: 996, four-stroke, liquid cooled, 90 degree V-Twin, DOHC, 8-valves, TSCC
Bore Stroke: 98.0 x 66.0mm
Compression Ratio: 11.6:1
Fuel System: Fuel Injection
Lubrication: Wet Sump
Ignition: Digital/Transistorized
Transmission: 6-Speed

also to note, in Hpower's engine performance kit for the superhawk, they use a 11.6:1 compression set of pistons just like the stock sv1000's, as they explain...
"Honda VTR 1000 Engine Performance Kit Piston Kit:
The VTR 1000 piston kit has a compression ratio of 11.6:1 and is designed to the same standards as the original piston which means you do not have to run extra piston to bore clearances. Pistons come with circlips, rings, gudgeon pins and includes new head gaskets."

 

That just may work as long as you have clearance for valves and the kit doesn't cost more then custom JE Pisions and rings...

Inlet = 1.3mm at 0.16mm valve clearance
Exhaust = 1.6mm at 0.31mm valve clearance

 

I kind of doubt it's a direct swap... There are a dozen small details that have to match up...