z175.. The good the bad and the ugly

[sean01]

ok i picked up a secondhand z175 not long ago with approx 10-20hrs (i think) on it, but was advertised as needing rings and blowing smoke..

i mainly wanted it for the bottom end only and wasn't fussed about the top end cause i'v had my suspicions on how long these engines will last..

ok so i put the z175 in my bike to replace a yx160 that chewed 1st, 2nd and 3rd.

the yx160 i took out had a v2 and s35 cam with a 30mm oko, i thought going by engine size the 175 would perform sorta similar but nope i was wrong big time..
the 175 was what i call gutless as and didnt have the torque that i thought it should, it didn't need rings or blow any smoke either. and had good compression.. and rattly as lol..

anyways today i pulled the z175 top end down to put my V2 on and hmmmm these engines are a mess lol.
for the amount of hrs on this engine the bore is stuffed and not from dirty air cleaners or anything like tht, and they dont have that much compression either..
the piston is down the bore nearly 2mm, and even tho they run a hi comp piston it wouldn't bring it up too much.

heres the pathetic compression height of the piston

heres the crappy short piston just like the early tb 64mm kits..

heres the stuffed bore, the shadows you can see in the bore are actual massive wear marks. the top of the bore has the nickel/chrome plate worn off (pretty much the same as every other plated cylinder iv seen for a china engine)

as for the rattle these engines get and the early tb kits, see this video lol.
i was amazed it still ran.. oh and there was a valve kiss mark on the exhaust side of the piston. probly caused by the piston rocking in the bore too much..
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid192.photobucket.com%2Falbums%2Fz263%2Fozconsoles%2Ftech%2Fz175%2520engine%2FVIDEO0013.mp4">

anyways lol my journey to fit the v2 went on.. this top end only needs to last the next parklands ride day so i wasnt bothers about the clearance issues it had..

as you can see in the video i had die grind the valve reliefs bigger to accommodate the lager V2 valves.

so i gave the bore a light hone and reset the ring gap placements, removed the basket and used honda bond instead to bring the compression up a little.
did a dummy assemble and valves cleared perfectly.
well until i started it up lol tho it was hard to tell if the extra compression has made the bore noisier or if its actually the valves kissing.. anyways lol couple of big revs and rattle is as bad..

like i said it only has to last the ride day, after that i will get the cases bored, shim the gearbox and fit the 67mm bore kit to it. oh and another set of valves lol..

anyways the end result was pretty good. heaps more power and rev to the moon again..much like my last yx160..

basically this thread is a word of warning that the z175's arent too bad of an engine but there not going to last as long as a z155/z160ho

and to let ppl know that V2's will fit on as long as the valve reliefs are made bigger..

another warning goes out to those in search of a secondhand z175.. you can bet the bore is stuffed..

oh and i remember there was rumor that the new z160/z175's had bigger valves, this is BS as the one i have here are the same as the older z155.. not sure what the chinese were thinking lol even in stock form the yx160's/z155 valves are too small..

IMO if i was buying a new engine i would be going with the z160ho, V2 and a bunch of goodies from akunar.. ie: bore kit, valve springs and clutch springs at the least.


thought i might mention too that these engines have far from 20hp, i doubt they'd have 1hp more than the z160ho.
..

 

[rach88]

My 175 have a few hours on it now. Been going pretty good. But I don't give it a hard beating. One ride of someone that has actually give it a beating and things quickly started going wrong ha ha.

 

[DHZ_XR8cing]

Good write up mate. I'm yet to be shown that any bore size bigger than the 155z/160 is of any benefit.

 

[sean01]

Good write up mate. I'm yet to be shown that any bore size bigger than the 155z/160 is of any benefit.

bore size can definitely be better mate, specially on a track that requires more torque.
besides to be competitive you need to keep your engine specs close to the class leaders lol

a well setup z155/yx160 with a 64mm bore kit, v2 and good carb a z155 has no chance.. even with a v2 and decent carb, they run out of steam early lol and not to mention the larger you increase the bore size the lower down in the rev range the cam comes starts to make its best power..so no need to rev the crappers out of it

 

[DHZ_XR8cing]

I love to rev the you know what out of them. I cant say the "T" word. Ill get banned again. lol.
I'f the bigger bore bike has more torque I would assume that means its peak power is earlier so therefore it shold pull harder but run out of steam quicker??

 

[sean01]

I love to rev the you know what out of them. I cant say the "T" word. Ill get banned again. lol.
I'f the bigger bore bike has more torque I would assume that means its peak power is earlier so therefore it shold pull harder but run out of steam quicker??

ideally you want them to produce more power earlier. revving them is what kills them..

and a bit of advice lol... revs dont make power, might make hp but torque is what you want..

but with a S35 cam they still rev like crazy..

the V2 head i recon has a perfect valve size combo for a around 180cc. up and over 200+ they could do with bigger again.

30mm carb also heaps bring some top end back.. not that your looking for it lol, its just good to have..

 

[DHZ_XR8cing]

I would like to see a good speed comparison done with the different engine configurations.
The big bore bikes give torque early in the rev range and this works great when mated up to a cam that is set up for it but the s35 seems to have a better torque curve higher in the rev range. I know its all about torque but also there needs to be decent rpm. Higher rpm = faster wheel rotations.
I understand that a high horse power engine with average torque is not much chop where as a high torque engine with good rpm is whats needed.
I spent a bit of time working with ford V8 engines and with them to get the most out of them when we bored them out they had to be de-stroked by putting shorter rods in them to get them to rev other wise all they were good for was towing.
These mini bike engines seem like they are a good combo with the standard 155 bore and stroke and I get the feeling that putting bigger bore kits on them make them to square.
I am not writing any of this claiming to be right. I guess its all curiosity really. Its more of a question.

 

[The_GDFP]

Nice post Sean. Sorta what I'd been saying. A $100 Alibaba big bore kit on a stocker ain't no powerhouse. We tested a Wiseco piston 195cc with a well-ported V2 and S35, PE28, CHP pipe and it was done pulling at 8500. (building a manifold and pipe, now) The chopped off skirt on that $17 piston is an afterthought, not designed as such like a Tak 67mm. The cheap platings used on the econo-bore kits can't handle the poor piston design rocking, and distorts to beat Hell when heated up on a little air cooled engine. I'll stick with quality steel sleeves, skirted pistons once the bore size gets any where near the studs.

A 150R has a pair of 26mm intakes. A single 30mm one is nowhere near enough for a decent overrev on a bigger engine. Old CB350 twin had 34mm intakes and wasn't a real revver. Bottom ends on these Chinese engines start absorbing all your power the faster you spin them any way. Let the midrange do the work. A smaller peaky engine feels fast, but a big one that pulls every where gets around a track faster usually. Just need to enlarge it CORRECTLY.

 

[sean01]

I would like to see a good speed comparison done with the different engine configurations.
The big bore bikes give torque early in the rev range and this works great when mated up to a cam that is set up for it but the s35 seems to have a better torque curve higher in the rev range. I know its all about torque but also there needs to be decent rpm. Higher rpm = faster wheel rotations.
I understand that a high horse power engine with average torque is not much chop where as a high torque engine with good rpm is whats needed.
I spent a bit of time working with ford V8 engines and with them to get the most out of them when we bored them out they had to be de-stroked by putting shorter rods in them to get them to rev other wise all they were good for was towing.
These mini bike engines seem like they are a good combo with the standard 155 bore and stroke and I get the feeling that putting bigger bore kits on them make them to square.
I am not writing any of this claiming to be right. I guess its all curiosity really. Its more of a question.

speed is the last thing you need to worry about when building a good track bike, sure it helps but not needed as much as power out of berms and trying for hole shots.

the s35 only builds torque hi in the rev range in the smaller (155) engines.. only thing that changes when fitting a big bore kit with the s35 is you bring the rev range down to a more useable level.. but also it may even add more to the top of the rev range as well, not that it is needed..

as to the high rpm = faster wheel rotations. its no good having high rpm if you dont have the torque to turn the wheel faster.. rpm is just like HP, nothing more than wank factor. but dont get me wrong you do need it, just not as much as most people think..
horsepower is from torque and rpm

yeah iv built a few 351 clevelands in my time, dont miss it either lol.. car engine work isnt my favorite anymore..
4.020 bore, offset ground stroke with the long 302 cleveland conrods and a good 600+tho lift cam(16mm lol) and grout fill the blocks to stop them from splitting bores used to make them go.. low 10's easy in the right car. add 300+hp nitrous kit and bust a 9sec pass in a cortina... brrrrr what a headache lol.. give me a chev any day..

The_GDFP
Nice post Sean. Sorta what I'd been saying. A $100 Alibaba big bore kit on a stocker ain't no powerhouse. We tested a Wiseco piston 195cc with a well-ported V2 and S35, PE28, CHP pipe and it was done pulling at 8500. (building a manifold and pipe, now) The chopped off skirt on that $17 piston is an afterthought, not designed as such like a Tak 67mm. The cheap platings used on the econo-bore kits can't handle the poor piston design rocking, and distorts to beat Hell when heated up on a little air cooled engine. I'll stick with quality steel sleeves, skirted pistons once the bore size gets any where near the studs.

A 150R has a pair of 26mm intakes. A single 30mm one is nowhere near enough for a decent overrev on a bigger engine. Old CB350 twin had 34mm intakes and wasn't a real revver. Bottom ends on these Chinese engines start absorbing all your power the faster you spin them any way. Let the midrange do the work. A smaller peaky engine feels fast, but a big one that pulls every where gets around a track faster usually. Just need to enlarge it CORRECTLY.

cheers mate..

yeah funny enough the more i looked at this 175 piston the more i convinced myself that it is just a long skirt piston machined down.. lol the gudgeon pin wasn't real easy to get out either..
i have a full skirt 65mm china plated barrel here and it wore out in just the same amount of time.. measured the piston up and its still in good condition.. still has a good taper lol.. i was amazed. but same crap quality..

i got another V2 here which needs new inserts, im thinking of going bigger in the valves or least in the exhaust anyways..

and yeah im with you on the steel sleeves.. i dont even like the bores on the yamaha's or any other jap engine lol..

 

[The_GDFP]

"Fire Power" came from the valve covers of the 51-58 Chrysler Hemi's I used to build a bunch of Pit bike engines are a Hell of a lot easier to load in the trunk, share a combustion chamber design... Spent a bit of time around pushrod V-8's too. LOTS more than the little mini engines, even.

Any way, a 33.4mm intake valve and a port to feed it properly may look some thing like this:

 

[rumble]

Is that your handy work?

 

[The_GDFP]

Notched one of the Alibaba's but didn't cut the skirt. ALMOST deep enough for a little float. lol

 

[darkrider]

so what your saying is the zog 175.. is **** compared to outher engines

 

[The_GDFP]

so what your saying is the zog 175.. is **** compared to outher engines

Nope, it's a so-so Z155 with a **** big bore kit installed

 

[wogtaz ryder]

Nice nice .

 

[sean01]

ok, my son and i couldnt help ourselves today and took it out for a floggin..

it lasted the whole day and is still running strong but likes to burn oil every now and then..(as i expected)

might have to resort to a stock 60mm barrel setup for parklands lol..

 

[coolmodee01]

yeah thats about right

but my 175 does go better than the 155's and yx's i've ridden i have had a bit of i tinker to

so tezza sean

what bore kit and head do you recommend on this donk?? i ask this as a motocross rider that rides alot in the mid range torque and not so much valve bouncing every gear change

i was gunna stick with the 170 with v2 but go a auto decomp s25 cam thoughts????


EDIT: worth a case bore or what??? also has anyone had a go at trying to get a clutch to last more than 6-10 hours

 

[The_GDFP]

Currently, the nicest BBK is the Wiseco forged piston. Notched for the V2 but not overly so. TB 64mm kit is great for the money, but the notches are a little deep for safety margin and assembly variations. Without substantial porting and a 32mm carb, a V2/+R headed mid-big build with an S35 is going to peak at under 10K. My own 195cc makes it's peak at 8700, but holds it to about 10,500 for over-rev.

Case boring is part of almost every build, so you can run the 69mm OD sleeve it takes to make a 64/65/66mm steel liner clear. You'll wanna be in there for trans and drum end play, any way.

Clutches should last a lot longer. That 17? with a stock head isn't a peaky 2-stroke. I'd give the same advice for your clutch lever as I'd give a 13 year old with a sore Willy: Leave it alone, 'cept for when you NEED it.

 

[coolmodee01]

hmmm food for thought there for sure

i did want to stick to something bolt on and stay reliable although i do like the idea of the wiseco gear they have a good rep in my hands.....i might just look at a bolt on 64mm from your nemesis at tb.
decisions decisions......

BTW in stock for i haven't had to much of an issue with my clutch in stock form my 6 plate lasted well over a year..... my mate on the other hand he is lucky to get 10hrs out of his but as you say he rub's it till it drops off

thanks tezz

p.s shimmed drums haven't had a g/box prob in 18 months with this engine

 

[The_GDFP]

hmmm food for thought there for sure

i did want to stick to something bolt on and stay reliable although i do like the idea of the wiseco gear they have a good rep in my hands.....i might just look at a bolt on 64mm from your nemesis at tb.
decisions decisions......

BTW in stock for i haven't had to much of an issue with my clutch in stock form my 6 plate lasted well over a year..... my mate on the other hand he is lucky to get 10hrs out of his but as you say he rub's it till it drops off

thanks tezz

p.s shimmed drums haven't had a g/box prob in 18 months with this engine

The 64mm TB (Mike at Honda Trail Bikes, a GREAT supplier, is not my nemesis. T-Bag, the half-witted parts *****, my arch-enema, now there's a different story)

The Wiseco is available in 64mm as well, slips in a TB jug, or steel-lined one with the spigot turned down.