10.5 to 1 compression?

[xsbobber817]

i read some where on here that a guy had 10.5 to 1 compression? how would you acheave that? im a 2 stroke enthusiest so to me i know how to do a 2 stroke head but a 4 stroke is a little more confusing, if some one could point me in the right direction that would be cool

i was also wondering where i could start a build thread? there is no xs or xj build section so should i post a thread under this? thank you guys

also got the xs unlocked, now im goin through the electronics then it will be ready to start

[DGXSER]

As to the compression ratio. Well, I have no clue, but look it up and you should see the standard, I think stock was closer to 9:1. I know some folks have stated more compression by installing the big bore kits.

As to a build thread, If it is an XS or XJ1100 then here is the spot. Some folks put them in the members lounge instead, but either one is no problemo.

[xsbobber817]

yur rite withthe stock compression ratio, but i swear i read a guy on hear had a 78 motor with 80 head that was ported and polished and 78 cams cuz they were hotter? he was building it for top end which makes sence but i still dont know how he got 10.5 to 1 unless he was runnning different pistons, or had the head milled, or had a thinner gasket

[Toolmaker Tim]

4000

Hey Don, congrats on your 4000th post!

[WMarshy]

yur rite withthe stock compression ratio, but i swear i read a guy on hear had a 78 motor with 80 head that was ported and polished and 78 cams cuz they were hotter? he was building it for top end which makes sence but i still dont know how he got 10.5 to 1 unless he was runnning different pistons, or had the head milled, or had a thinner gasket

I dont think thats quite right... The 78-79 pistons have less dome to them than the 80-81's. The after market big bore kits dome is between the two versions. From what I have read, using the 78-79 heads with the big bore kit should give the most compression out of all the combinations. I dont recall reading about any clearance issues with any of the big bore kits with various heads. You might want to let people that have first hand experience with the kits chime in...

As far as the cams, the 78-79 are the 'hotter' ones...(more lift & durration? IDK the specifics). But from a performance stand point I recall someone useing a 80-81 head with a 78 intake (or exhaust, cant remember syr) cam only. Dan Hodges is the person you want to read up on, he has tried and proved what works and doesnt...

[XS1100_OEM4ME]

compression

9.2 to1 covered most if not all xs1100 years. If the guy you talked about did a port/polish job and went higher comp. he most likely did some milling of head and pos. cyl. You can also add materal to the combustion chamber to mod. air flow/compression but most likely it would have been a change of pistons to hi preformance racing ones. If you bump it up with todays gas, knock and other prob's will show up, are you going to race only or street?

[XS1100_OEM4ME]

1100 spec.

Here is a likk to xs1100 spec/year's

http://www.xtreemedecals.com/yamahai...yamaha_xs.html

[WMarshy]

The higher content of Ethanol actually should work better in higher compression engines...

[xsbobber817]

a little bit of both street and racing. im reading up on performance mods for these things, and it looks like theres not to much motor wise to be done. there isnt hot cams available still, no stroker etc etc im just trying to find the most semi stock power possible, and more cost effective too than some of the stuff thats available.

[DGXSER]

Thanks Tim on the congrats...at this point its kind of like your 40th birthday...just another number by that point.

If you search for post by Dan Hodges, you will find ALOT of info on what cams work best with what heads and such. That guy has tried them all and has documented the results with measured and dyno information. When it comes to making power with these engines, I have met no other who has more info. Here is an example of a good thread on power from these beast.

The only thing I recall seeing about making higher compression was from folks who have installed the bigger bore kits which include pistons.

[Rstyduck]

Wiseco Pistons claims theyre big bore kits bring your compression up to 10.25.

[natemoen]

I think I remember reading 81xsproject's tech thread about his Megasquirt EFI build talking about how he used a 78 exhaust cam with the 81 intake (might be the other way around). I think he has the big bore as well on his bike though and he got the 10.25:1 comp. I do remember him talking about how he was following Dan Hodges lead with the EFI though. As stated read Dan's post, he is the man to talk to for power. He had tried everything under the sun to make as much power with these beasts.

A good way to get power though is to go EFI. Its a lot of work but it produces results just by giving you a better and more accurate fuel/air mixture. It can be expensive if you buy all the parts but it can also be pretty cheap to do if you make the parts and scrounge for used stuff.

[mro]

there isnt hot cams available

Actually there still out there, but hard to find ...
I meet a guy yesterday who says he has a set of mega-cycle cams for the XS w/adjustable sprockets.
I wasn't interested because I already have a set

If anyone’s interested PM me with your phone # and I’ll pass it on.

mro

[81xsproject]

I think you can still send your cams off to Web Cams. I also think that APE will weld-Grind your cams as well.

As for myself, no big-bore (yet), and I only wish I had ten and a quarter. I do run the early intake cam. It DOES make a noticeable difference. I have also run both early cams in my late head which does make a even bigger difference. Unfortunately, with both, the difference is noticeable in both the top and bottom end, if you know what I mean. However, with these bikes and the way I ride, I don't care that much about the very low end and am still considering going back to both early cams.

As far as I know, Dan doesn't not have EFI. I have picked his brain on several occasions. He is how I arrived at running just the early intake cam. He also gave me some info on how I might set up my fully adjustable timing curve. I just hope someday we get to hear what ever happen to his 1311cc XS build that he mentioned.

[yamahansolo]

Ok they aren't all 9.2... 80 and newer is only 9.0 to1. And mega cams still makes cams for our bikes and there is at least 2 size big bore kits still available not sure where you heard no cams or piston kits???