cams

[lparker]

talking about 80s cams travel alot on my 78 motor 79. is it enoughf of a boost in midrange to be worth it. on hwy running over 5000 rpm im not worried about power its hwy patrol i look for . have a 1198 kit in it now lots of piston rattle dont know how many miles on eng was replaced . does anyone know where you can by stock pistons i have extra set of cyls. taking 2500 mile trip this summer it runs good now but i dont trust it

[81xsproject]

do a search. I swear I just saw a post the other day that someone had a brand new set that they got and then changed there mind and got a big bore. Maybe it was ebay, I can't remember.

[81xsproject]

Here you go.

[lparker]

thanks i am going to bid on them

[pggg]

Park, the 78' 80' cam difference isn't huge but it's noticible as the motor is conveniently flexible for twisty and hilly roads(80' cams) but going down from 1196cc to 1100cc you'll probably feel a drop in low rev grunt anyway.

[lparker]

i will prob loose some power going back to stock bore but i can get rid of the piston slap and the very thin cylinder sleeve. with the heat we have in center of Florida and the fact that when i go for rides that are about 300 miles most every weekend (getting back side in shape to ride it to sturgis 1st of Aug.) heating up might be a worry. comp with the bore kit is 125 to 130 seems Low To me most bore kits i have delt with were about same or a little above factory specs . with higher comp may mot loose as much power as i think.

[pggg]

I wouldn't worry about the heat there's no way in hell you can blow it up. It's only a couple of mm's different. Not sure on this, but I heard that if compression ratio increases, it doesn't neccessarily mean the compression reading will increase also.

[TopCatGr58]

Don't get slapped around, get bored!

Hey Lparker,

First sorry you may have already started bidding on those pistons, cause IF they are OEM size and not any oversize, then you could have some trouble! The spare cylinders you have, are they already used OEM size?? If so, then unless they have extremely low amounts of wear, you may NOT be able to use the new OEM pistons, cause oversize rings are not available!!

What ARE AVAILABLE are new rings for your 1196 pistons, along with new wristpins, and you could bore out your spare cylinders to 1196 and go back with new rings and wristpins and would have a FRESH and still powerful engine!

Your comp levels do seem rather low, cause with just my 1179 kit, I obtained over 180 psi after breakin!! Mine also does run just a little warmer than oem, but unless I get stuck in total stop and go traffic, it works just fine, have run many 500-1000 mile runs to rallies over the past several years with no problems at all!!

[lparker]

havent bid yet was waiting to see where price went . thrust bearing loose going to replace all crank and rod bearings but that isnt a problem yamaha still sells them wish thay still sold pistons .it would be nice to keep the bore kit ape still lists the big bore kit. a lot of harleys around here would like to see it go back stock . sat down at the lathe and mill day before yesterday made a new mounting plate and rotor it now has a fj1100 ign system big improvment dont have to think about pick up problem any more ape also does trans under cutting think im going to send one off . has anyone ever tried to shave the cam bearing caps to tighten them up a little ? mine is at outside limit but i dont know if i can get away with it.

[DiverRay]

If you shaved the cam bearing caps, you would have to do all of them, and the head. Tou would then need to run a ream to bring it back round, and the proper size.
Ray

[TopCatGr58]

Hey Lparker,

You've got to take some photos and post them and specs on this FJ1100 ignition MOD for ALL OF US!!

Secondly, if after you've had the cylinders miced to check for wear, out of round, etc, and IF they are still within spec for going back with OEM pistons and rings with just a honing, I've got a set of 4 oem pistons that I'll be willing to let you have for shipping!! Since I put my big bore kit in, I don't need them anymore!

I just checked, and the Standard size OEM Piston Ring set is still available from Yamaha/bikebandit, etc, around $37.00!

My odometer had broken after 900 miles when I first got the bike NEW in 83, broke it in gently, and drove it responsibly for 9 years, estimated 50k on pistons, but again, hopefully that's mostly wear on the old rings vs. the piston skirts!?
T.C.

[lparker]

just a thought for what line honing would cost i can replace the head

[lparker]

will take some pictures used a extra vacume advance holder and cut it down on lathe to make a plate to hold pickups then made a new rotor to trip it timeing was the hard part to get right . dont remember weather fj is a counter clock or clock motor but the pickups dont care adv works good it goes by what the pickups say

if works out good ill draw up plans for adpter and rotor and let you have them for poeple with out a lathe i can make them a set if thay get there one elect parts

[lparker]

T C do you think late mod cams are worth doing

[TopCatGr58]

Hey LParker,

I'm no Engine guru, PGGG, Dan Hodges, and others have much more knowledge about hopping up the engine. The later year cams appear to have a longer duration, but less lift! I have an 81 machine with stock cams in my 1179 machine. I think it has plenty of punch down low, as well as thru the entire rpm range. But I've got the larger valves also. With the smaller valves of the earlier head, it might provide a little better boost due to longer duration, but it might just balance the fact that it has less lift than the earlier cams!? Sorry I don't have the definitive answer you're looking for!
T.C.