Upgrade yx160cc bore kit?

[DustyFork]

Hey all I'm looking to upgrade my 160 to get a bit more power. As I carnt find anyone selling some used big bore kits I thought I'd just go new. My engine is stock except for a machined down Adjustable ORK and I have an oko 28mm on it. Been looking to upgrade the bore first then the head. What my problem is do I get the 184cc big bore or can I get the 201cc. I found the best price at firepower minis. What should I get? Any ideas?

 

[Styv_Loosekid_21]

What ever bore kit you get make sure you specify that the piston you need needs to match a stock yx160 head

You can get all the way up to 184kits but the 201 needs case boring and that cost more spundoolie.. If I was you I'd by the 184kit with v2 head and hold on!! Cause it literally goes from mild to WILD!!

 

[zwebx]

you can go to a 184 kit from tbolt usa no problem like installing a stock bore..
anything over that size requires a split case and then case boring

i may reccomend going to a tbv2 head if your looking for more power then bigbore but do it in any order the 184 will increase your torque throughout but i reckon a head if you have the cash is the way to go
Edit ^^ great minds think alike.. but dont type at the same speed

 

[DustyFork]

Thanks guys the v2 head is what I want but I carnt find one cheap. Not sure how much they are just seen a few for about 370. I m thinkin get the bigger bore and keep hunting for a head and a better used cam to get me by till I get the head

 

[zwebx]

Thanks guys the v2 head is what I want but I carnt find one cheap. Not sure how much they are just seen a few for about 370. I m thinkin get the bigger bore and keep hunting for a head and a better used cam to get me by till I get the head

the tb v2 heads are 440 with a tb stock bore piston i would not go a second hand head nor bore unless its running and decently cheap
you certainly dont want to go a 2nd hand bore or piston because they are service items..

if you want a cheap but decent build hit up akunar.com ask him for the prices i think it was 115 for a bore + shipping from taiwan but is still pretty cheap

 

[lets ride]

mate speaking from experiance and lets say alote of money , i have a stock 155 with a v2 head and im pritty happy with it but i do want to go the full 177 , id say save ur money and buy all new parts mate because it could cost you more in the long run

 

[zwebx]

mate speaking from experiance and lets say alote of money , i have a stock 155 with a v2 head and im pritty happy with it but i do want to go the full 177 , id say save ur money and buy all new parts mate because it could cost you more in the long run

if your going to do that you may want to get the tb s25 cam instead of the s35 cam to spread the power from mostly up top to nice and low/midrange

 

[lets ride]

i personaly like the s35

 

[DustyFork]

I'm back with a new tb v2 race head, new 60mm high comp piston and decomp add on. I fitted head and tunned carby. Not too much diffrence in power but its good in top end. I line it up beside my mates stock 160 and test the diffrence. I went with the s35 cam but thinking the s25 might suit me better. I do more trail riding then anything. I'm looking to do the bore now I need more power! Been looking for info on the 67mm bore upgrade and to see if the results of using this bore size to the 64mm is much better. Keeping in mind the 201cc upgrade needs case boring which costs more and more labour. 184cc and 201cc bores are same price. Has anyone done 67mm upgrade? What problems may occure from this upgrade. And what do I also need to upgrade such as clutch ect. Too many old threads need fresh new info as more people by now have done 67mm upgrade.

 

[zwebx]

kosta has the 67mm kit i have had a ride, he races on it its a tractor (will never need any more power)
64mm, increase in power and is nice to the transmission because it has a little less tourque
67mm, major increase of power (hard to keep the front end down on a lxr and thats saying somthing) will require more throttle control for the trails and also will require probably a better clutch basket billet or change your one with a new cheapie every time its necessary there really quite mean to the transmission when you go over 64mm

i reckon you would be happy with a 64mm personally its all the usable power that you would need and has been proven to be quite reliable..
the 67 will be all the power you want (maybe a bit more)along with the transmission issues in the long run.. and also clutches dont like the power so you may need stronger clutch springs and kevlar plates.. but you will always be busting the stock baskets or atleast the rubbers in the basket (can be modified so they are serviceable)

 

[DustyFork]

You've got me grinning from ear to ear with the comment about the 67 being too much power! I am a bit nuts and love to much power it's just being able to tame it which I will do with gearing. Do you know of the type of transmission problems. I don't know much about tranys on bikes, I read some older yx are weaker then new yx engines tranys and some stuff about shimming and what not. It was not quite clear on what they where going on about. Anyone know?

 

[zwebx]

You've got me grinning from ear to ear with the comment about the 67 being too much power! I am a bit nuts and love to much power it's just being able to tame it which I will do with gearing. Do you know of the type of transmission problems. I don't know much about tranys on bikes, I read some older yx are weaker then new yx engines tranys and some stuff about shimming and what not. It was not quite clear on what they where going on about. Anyone know?

3rd gear is the main problem, sometimes the gear strips.. or a bearing blows along the countershaft or anywhere really
there are more things that can go wrong but that is what i hear the most..
there simple things and are cheap to replace 140 with new shift drum but require the cases to be split so is a *****..

 

[DustyFork]

I'm planning to replace internal bearings with quality ones when I pull it down for case boring. Any thing else I should replace or strengthen while I'm in there?

 

[zwebx]

depending on the wear maybe the whole gearbox.. make sure the shift drum is in good order too (looks smooth and not to warn)
the rest eg clutch and all that can be changed quickly no problems

 

[my67xr]

as zac suggested above,
check the gears for chipping, worn teeth, worn dogs, and worn shafts.
i'd be fitting a decent oil pump in it while it's apart too, do you have a good quality timing chain for it ?

it might pay to source a gearbox shim kit, it'll probably come in handy when it is time to reassemble it.

 

[DustyFork]

Gee it sounds like going to a 67mm bore ain't easy and cheap but will be a good learning curve and project. I think I'm gunna need a doner engine as it may take a little to build and the means less riding time. I've never done a bottom end on a motorcycle engine so more time taking to learn that too! Well I guess I'll start collecting the bits then

 

[Phil67]

What kit are you buying? Leave the base gasket out, just use Honda bond or similar, or machine 7 thou off the jug, same effect. Gives you slightly better comp. if you are using the TB kit, be careful using a stock head, check clearances well. Yes replace shift forks for sure, maybe drum as well. Usually second gear is dodgy, dunno about third. I've done second twice and 2 shift forks with the 63 kit.

 

[zwebx]

What kit are you buying? Leave the base gasket out, just use Honda bond or similar, or machine 7 thou off the jug, same effect. Gives you slightly better comp. if you are using the TB kit, be careful using a stock head, check clearances well. Yes replace shift forks for sure, maybe drum as well. Usually second gear is dodgy, dunno about third. I've done second twice and 2 shift forks with the 63 kit.

i reckon you will have enough power without going to extreme tolerances unless your goin for a land speed record i reckon the tb pistons already have a crazy amount of compression and its nice knowing things have some room for error, or wear (still cant believe how long some of the engines last in this configuration)

once you have split the case dusty fork you will wonder why you have feared it its quite easy.. just time consuming (kinda like opening a for you think it would be heaps finiky but turns out its quite simple) the most annoying thing is shimming the gears and thats not even to bad (if you only have to do the shaft not a individual gear..)