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General Category >> Rubber Side Down! >> 97mm Big Bore
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Message started by DragBikeMike on 03/25/18 at 02:20:58

Title: 97mm Big Bore
Post by DragBikeMike on 03/25/18 at 02:20:58

Any of you done the 97mm big bore? Any problems with detonation? Any problems with starting? Any problems with seizing? Any problems with vibration? What does the 97mm Weisco assembly weigh in comparison to the stock assembly?

Title: Re: 97mm Big Bore
Post by Dave on 03/25/18 at 04:00:14

All of the Wiseco pistons are very close to the weight of the stock piston.

You need to run premium, and if you do there are no problems with detonation.

I am aware of 2 forum members who went out on the interstate and rode at sustained 75-80 mph speeds prior to the piston being properly broken in.....and the siezed the piston. There is also one member who recently had a 97mm sieze when the cylinder was not bored properly - his new 95mm Wiseco is behaving well so far.

You need to keep an operable compression release if you go with a Wiseco. You may not need it every start.....but once in a while the piston comes to rest on the compression stroke, and the starter cannot get it over TDC without the advantage of some rotational inertia that the compression release provides. (The compression release only works for 1 or 2 rotations of the crank).

The difference in HP from the 94mm to the 97 mm is only 2-3 HP - you can install the smaller 94mm in the cylinder without boring the cylinder oversize. (I am running a 95mm and it works great).

Title: Re: 97mm Big Bore
Post by Christof13T on 03/25/18 at 08:03:58

My 97mm piston build was a vast improvement over stock... until it failed at 183 miles...
It is now the 95mm Dave just mentioned and by my SOTP Dyno there are no noticeable differences between the 97mm and the 95mm. If I had to do it over again... I would opt for the 95mm. I still can't justify the extra $ for a stock bore high compression piston vs the cost of punching it 1mm with the bore work to mate the piston anyway. Especially if one intends to have a coating applied to the bore.

These are fun little bikes... But definitely no drag racing contenders. That is unless of course you intend to only race other Savages...
It has taken me weeks worth of the little bits of spare time I get to coax my 95mm build to the 80mph mark. I think I finally found that magic combination just this morning...

Title: Re: 97mm Big Bore
Post by Fast 650 on 03/25/18 at 10:18:48

The seat of the pants dyno has one thing that is almost as accurate as a genuine dyno... A 10% difference is about the minimum that you can feel.

A simpler method to measure your gains is with one of the 1/4 mile time smartphone apps. Do a before and after run and you have a record of the difference then.

Title: Re: 97mm Big Bore
Post by Fast 650 on 03/25/18 at 11:14:41

6F445E455F58434A1D1F782C0 wrote:

It has taken me weeks worth of the little bits of spare time I get to coax my 95mm build to the 80mph mark. I think I finally found that magic combination just this morning...

Assuming that you are not gravitationally and aerodynamically challenged, and that you are not at 20,000 ft elevation, you had something way out of whack if 80mph was hard to reach. 80 in 5th is barely 5000 rpm, just past peak torque.With everything right, you should be able to reach 75 in 3rd easily.

Title: Re: 97mm Big Bore
Post by DragBikeMike on 03/25/18 at 11:50:09

Thanks to all for the good info. Christof13T, do you have any additional info on the failure? Was it a seizure, wrist pin, etc.? I'm curious why you state that the 97mm is only 1mm larger than stock. Isn't the stock bore 94mm? That would make the 97mm overbore a 3mm increase.

Title: Re: 97mm Big Bore
Post by Dave on 03/25/18 at 14:10:07

The stock size is 94mm....and Lancer sells a Wiseco in that size and they are made for Lancer on a special order, and Wiseco doesn't stock them.

The next size up is 95mm, and that is the stock size for the DR650, which is why we have a piston option (Wiseco doesn't make it for the Savage....it just happens to fit).

There are also 96 and 97mm sizes available from Wiseco.

Title: Re: 97mm Big Bore
Post by Christof13T on 03/25/18 at 15:08:11

494F403C3E393D0D0 wrote:

The cause of the factory build failure is still undetermined.
Suzuki said it was the result of a "Cold Lock"... but the failure occurred at 80mph going uphill after already been riding for a good hour...

The piston has evidence of potentially being a bad casting... but without access to a qc lab i can't prove it.

The 2nd failure was on the 97mm rebuild.
Something screwy happened with the boring process that left the cylinder egged, tapered, and oversized. After the failure and subsequent teardown... a circumferencial crack was discovred in the bore on the exhaust side right at about 12 O'clock... 2" from the bottom of the bore. The fellow that did the cylinder work put in a new sleeve from L.A. Sleeve and bored it to fit the 95mm wiseco and carbide coated the cylinder.

My issues of not being able to break 80mph seem to be cured. I had a spare carb laying around, so I cleaned the heck out of it and set it up for middle of the road jetting. I'm sure the other carb just has a clog somewhere..