XJ1100 big bore piston kit

So I needed to rebuild my engine because of others mistakes. I ordered a big bore piston kit as I couldn't find new standard pistons anywhere. Will be a1200cc when done. Took a very long time to find a shop that will bore and match the pistons to each cylinder. Just got a call from the shop telling me my cylinder holes are 120 thousands oversize. I've seen someone here did a 650 big bore kit for their bike. Anyone ever have any issues after a big bore install?

 

Well no answers for that question how about this one.... is a rejet necessary with a big bore install?

 

I'd try asking over on the XS/XJ forum here>Forums - XS11.club Forums Basically your XJ1100 engine is just a XS1100 with YICS.

 

Common sense, but no experience of this conversion answer from me - if the liners are thick enough no issues. Will you need to rejet - probably yes, the trouble is it will be mid/high speed and load jetting, which is difficult to feel, so you need to take a stab at bigger mains, bigger idles as well, and do plug cuts. For referance my 750 runs fj600 carbs without any jetting changes - it absolutely flies, but my "feel" is it needs bigger idles.
In short I wouldn't be concerned.

 

Also I have no experience with the XJ1100 however Yamaha took the FJ1100 and bumped it up to the FJ1200, later an XJR1300.
Find out what changes they made to the carbs through this process, it might be useful.

I read an interesting article in Cycle World by Kevin Cameron discussing this subject.
Surprisingly some cases actually require smaller jets but those were not CV carbs.
Yamaha jetted the XJ750 richer than the XJ650 and different needles, same basic carbs so this can provide clues also.
I would agree with @Minimutly initially go bigger just to be safe.

 

Carbs went from 34mm on the XJ1100 up to 36mm on the FJ's and early 13's then up to 37mm before FI.

 

So if both FJ1100 and FJ1200 had 36mm it might be useful to see what they did.
I'm curious.

 

So, all carbs, whether cv/cd or not, use airflow to suck fuel out of the float chambers. So to be over simplistic, if the carb is the right size for max airflow, the fuel/air ratio should be about right. But of course life is never that simple - the carb will have a "slope" - where idle,progression,slide spring and needle emulsion tube, then main jet comes in. Engine capacity, rod/crank ratio, air box capacity will all affect this, as well as cam timing and cr.
Start richer is the best advice I can give, at least that's safe.

 

Thanks for all the great replies! Definitely gashes me a place to start. Maybe track down some FJ carbs. I'll certainly try looking for a jet kit if there's one available

 

Ok. Revisit... if the fj1100 and 1200 were basically the same motor as the xj1100 then wouldn't the carbs from such bolt right on? Or if the same carb but upgraded , then a repair kit for the fj carbs may fit and work on the xj carbs.

 

Sorry i've only just seen this.
The only comparison between the XJ/XS1100 engine and the FJ's is the fact that they are 4 cylinder oil/air cooled.
The FJ's are 16 valve heads, the XJ's 8 valve heads. The carbs are similar like you say, but you'll need kits for the later type carbs that are fitted to the XJ1100 or XS1100 Midnight Special, early XS1100 are different. If you do get repair kits make sure that you get genuine Mikuni. Keyster and the like are rubbish.

 

If I'm reading your post correctly, the machine shop is telling you that the cylinders are already .120"/3mm over-size from the standard 71.5mm bore spec. At some point in the past the engine had already been apart and max overbore installed. If your cylinder walls are now damaged or out of round beyond the allowable skirt clearance for the 74.5mm pistons, then you'll need to find a new cylinder block as yours is now a fancy door stop. If it's still in spec, then new 3mm oversize pistons should slip in with no issues and if your bike was running ok before, then the jetting had been adjusted for the oversize prior to your ownership.

 

I've actually come across dyna jet when talking with a local reputable shop owner who recommended giving them a try. I did contact them and they can build me s specific set of jets for my big bore build as long as i give them my specs so I should be ok.

 

The machine shop thought I ordered the wrong pistons and were worried about the walls becoming too thin. They brought me in to speak with the machinist personally and we cleared up the misunderstanding. The block was stock never touched and I told him I ordered those specific big bore pistons because no stocks were available anywhere not used or within my sight to measure. He went ahead and bored to the minimum clearance of .0020 in and they were pleased to see that wall thickness was much better than anticipated. So now after a valve job and some mild clean up porting reassembly can move forward.

 

I'm new here my first post, and I have a few questions.

I have a XS1100 with the 71.5 stock bore and I've sourced a +3mm big bore kit for it. My question is will the head & cylinder block with the stock bore of 77mm from a FJ1200 fit on my XS1100 cases. I do realize case boring would have to be preformed.

I like the longer stroke of the XS1100, and using the +3mm big bore kit would bring the cc's up to 1196cc from it's stock bore & Stroke configuration. It appears by using the bigger bore cylinder block of the FJ1200 with it's 77mm stock bore and the crankcases of the XS1100 I'd have a big bore stroker engine that would bring me up to speed with the 1400's being produced today.

I'm not wanting to go the newer bigger engine route on account I like the older air-oil cooled engines over the water-cooled newer versions.

Question . . . if none of what I've mentioned above will work who might I get to revalve with bigger Intake valves, port and flow head for use of bigger cams for a better breathing Natrally Asperated Engine.

Before you all barbecue me on this, please ask me what I'd like for my last meal before you all kill here lol lol

 

The FJ crankcase studs are a different configuration to the XS, i know because i've got both bikes albeit the FJ is in XJR form.
You might want to consider using a cylinder head and pistons from a later model XS as they had bigger valves and higher crowns on the pistons.