Big Bore Kits

[Anonymous]

I'll get to my point:What are the pros/cons of the infamous 'Big Bore Kits"?We've all heard of them at some point,now I'd like know more.
Who makes them?What is involved in the conversion?How big a bore is too big?Is the hassle worth it?Can a guy install it himself?
I have a low mileage 86 750 that is in good running condition.Not that I'm contemplating doing it,but if I do,would it be a case of "if it ain't broke,don't fix it"?
Any insight on these?

 

[Anonymous]

Big bore kist

Big bore kist

You must decide first if you want to split the cases and have them machined or if you want to just work on the barrels alone

 

[Anonymous]

Big Bore Kits

Hi,Scotty,
Let's just stick to the barrels.If I was to do anything,I'd leave the bottom end alone.If the motor had some serious mileage on it,then I think it would be prudent to go through the whole motor, but having low km's,I would'nt do it ($).
-Paul(Gitch)

 

[Anonymous]

IF YOU LOOK IN YOUR BOOK IT WILL GIVE YOU THE SERVICE LIMIT THAT YOU ARE ABLE TO BORE THE ENGINE TO--ON MY 1100 IT IS 3MM I WENT TO 10.25 TO 1 COMPRESSION BUT I THINK I COULD HAVE GONE A BIT HIGHER AND STILL EASILY RAN ON STREET GAS- ON A SMALLER CC BIKE IT SEEMS THAT YOU CAN RUN HIGHER COMPRESSION AND STILL SUCCESFULLY RUN ON HIGH TEST-ASK THE SPEED SHOP PEOPLE AND DONT BELIEVE EVERYTHING ANY ONE TELLS YOU-THERE ARE MANY VALID POINTS OF VIEW ON COMPRESSION-- AFTER YOU DO THAT YOU WOULD BE VERY SMART TO HAVE THE HEAD STREET PORTED WHILE THE ENGINE IS APART-I DIDNT AND WILL REGRET IT WHEN I HAVE TO PAY LABOR A SECOND TIME--IF YOU HAVE THE BUCKS YOU SHOULD USE ADJUSTABLE CAM GEARS AND HAVE THE CAMS DEGREED WHILE THE BIKE IS APART-YOU CAN GET LOTS OF EXTRA PERFORMANCE FROM STOCK CAMS THAT ARE PROPERLY TIMED--ANOTHER MISTAKE OF MINE. THE CARBS CAN BE TUNED AND GIVE YOU A GREAT DEAL OF PERFORMANCE FOR THE COST OF A FEW JETS AND A COUPLE OF WASHERS IF YOUR MID RANGE NEEDELS ARE NOT ADJUSTABLE----BUT BUT BUT IF YOU DONT PUT ON A PERFORMANCE EXHAUST FIRST AND ARE NOT WILLING TO PUT UP WITH THE AGGRIVATION THAT GOES WITH PROPER TUNING, THEN LEAVE THE BIKE STOCK BECAUSE A 750 IS ALREADY A FAST BIKE WITHOUT ANY HOPPING UP-THIS IS JUST ONE OPINION YOU WILL GET MORE AND THEY ARE USUALLY ALL VALID

 

[mikegs1100ez82]

Scotty made alot of fine points. See what all can be done while you have it apart. Don't pay for labor twice if you can help it and reserch who you have do the work. I suggest you get a written estimate. Lessons learned.
Good Luck Mike

 

[Anonymous]

As someone who's fitted a big bore kit, I can only agree with Scotty, except to add that the performance gains are well worth having IF thats what you want.
I did the conversion myself, just a straight forward 3mm overbore and then rebuild. I saved myself a lot of labour cost which may have made a difference to the cost/benefit thing.
The bike now runs a lot better all through the range. Much more sprightly and less asthmatic. Its as if this is what the big 'S' intended, but the need to cater for the global market made them back down a little on the CR.
On the other hand, if I had a 750,I'd probably trade up to the 1100 before going down the big bore route, the overall costs would work out the same.

Incidentally, can anyone answer my post about the GS1000 1085 kit elsewhere?

 

[Anonymous]

After stripping down an 1100 engine, that I picked up, I found that it had "dry siezed" (she had sat around outside for a couple of years with one plug missing) I took a 2 mm cut out of the bore and used a wiseco kit which gave me 1135cc (same as the 1150) it revitalised a slightly tired engine which has, after fitting it to my beloved, been going fine for the last 20000K. It certainly has a fair bit more grunt now than the other engine which is getting a bit of a tidy up as well. The trick is to get someone who knows what they are doing with the machining as I have heard some horror stories. If the bore is the only thing you do then you will not need to rejet.