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Discussion Starter #1
I'm toying with building a bigger engine for a project I'm doing.



Does anyone know of a way of getting around 8 to 8.5:1 compression ratio with a 160cc + motor, the bigger the better.



Thanks
 

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It is possible but you won't like how you do it. You can either find yourself a dished piston, one with a lower deck, or swap the connecting rod.



Option 1 - Dished piston. I think this is the best solution there is. That way you get the best flame propogation instead of having the piston in the hole. Cheap too...if you can find a piston.



Option 2 - Lower Deck. A cheap solution but unlikely to find a lower deck without compromising the ring landing.



Option 3 Swap the rod/crank. Probably most expensive. Find a 57mm crank and swap the rod from a 53mm crank and you've essentially dropped the piston from deck into the hole 2mm. Then, adjust your base gasket to dial in the ratio how you want it.
 

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fatcaaat said:
It is possible but you won't like how you do it. You can either find yourself a dished piston, one with a lower deck, or swap the connecting rod.



Option 1 - Dished piston. I think this is the best solution there is. That way you get the best flame propogation instead of having the piston in the hole. Cheap too...if you can find a piston.



Option 2 - Lower Deck. A cheap solution but unlikely to find a lower deck without compromising the ring landing.



Option 3 Swap the rod/crank. Probably most expensive. Find a 57mm crank and swap the rod from a 53mm crank and you've essentially dropped the piston from deck into the hole 2mm. Then, adjust your base gasket to dial in the ratio how you want it.


Actually the 57mm cranks have the shorter rod than the 53mm cranks.



The TB cylinders are taller than the standard YX cylinder and so this would lower compression, on a BBK run the akunar piston and it will sit lower in the whole.
 

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I'd go with the 'caaat's suggestion of a dished piston, with a decent quench area. Without static compression, the chamber gets lazy, and a decent quench area will excite things enough to keep from requiring a ton of ignition advance to have decent torque. You can even get away with a little more compression, compared to leaving the piston in the hole. There's also sinking the valves and re-unshrouding them, to gain chamber volume. Plenty of 4v engines have a short compression height and dished head, allowing added stroke, too. Just need to add a set of notches, at worst. I have one with a 70mm bore and moderate compression. Easy on kicker gears, and my junked ankle.



More info on the plan would be helpful, and ease my curiosity;)
 

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Discussion Starter #5
Thanks for the suggestions guys.



So I'd be looking at a Zongshen 155 bottom end, an Akunar piston and a TB jug, do you have any part numbers for the TB & Akunar parts.



I haven't purchased anything yet, it's still in the planning stage.



How are these Z155's holding up so far?
 

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Discussion Starter #6
firepower354 said:
I'd go with the 'caaat's suggestion of a dished piston, with a decent quench area. Without static compression, the chamber gets lazy, and a decent quench area will excite things enough to keep from requiring a ton of ignition advance to have decent torque. You can even get away with a little more compression, compared to leaving the piston in the hole. There's also sinking the valves and re-unshrouding them, to gain chamber volume. Plenty of 4v engines have a short compression height and dished head, allowing added stroke, too. Just need to add a set of notches, at worst. I have one with a 70mm bore and moderate compression. Easy on kicker gears, and my junked ankle.



More info on the plan would be helpful, and ease my curiosity;)


What I'm trying to achieve is to turbocharge an engine for my Monkey bike.



I have a suitable fuel system, I've gone the Microsquirt ECU route and used some Honda parts for the throttle body, fuel pump etc - I have this mounted and running on a sacrificial engine, I have a wideband 02 sensor setup too - so no nasty carb jetting issues when it comes to tuning.



The Turbo is a Mitsubishi TD-02 sourced from States, originally destined for a Suzuki 660cc car, hence my quest for as many cubes as possible with a reasonably low compression ratio - to get it spinning.



I must stress I am not doing this to make a huge amount of power, more for the actual 'doing of it'
 

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Aaaah. Turbo and EFI makes the quench issue a non-issue, pretty much. Lots easier to source a big flat top piston and leave it in the hole.



The only Z155's I've seen were holding up OK, besides the inherent design flaw of the wobble-basket. Ho's aren't any better, in that aspect.
 

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Discussion Starter #8
firepower354 said:
Aaaah. Turbo and EFI makes the quench issue a non-issue, pretty much. Lots easier to source a big flat top piston and leave it in the hole.



The only Z155's I've seen were holding up OK, besides the inherent design flaw of the wobble-basket. Ho's aren't any better, in that aspect.


Excellent news.



The wobble-basket issue: Is this the same clutch basket tolerance issues that were in the original 160's?



Please excuse my ignorance on these matters, we seemingly only get the latest stuff in the UK when it's a good-while-old
 

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MonsterMonkey said:
Excellent news.



The wobble-basket issue: Is this the same clutch basket tolerance issues that were in the original 160's?



Please excuse my ignorance on these matters, we seemingly only get the latest stuff in the UK when it's a good-while-old
They all have a wobbly basket,,YX,Z, HO etc, even the Daytonas,they have just a little less.

The z engine as well as the HOs use the same rod length as the 53 stroke YX 150s , so those come up 1mm more to the top , this would add more compression.

I might suggest a YX 160 crank for more stroke but letting the piston set down 1mm in the hole.
 

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Discussion Starter #10
Thanks for the suggestions guys. I seem to be struggling with UK suppliers to get what I want.



I imagine shipping motors accross the pond would be an expensive affair due to weight, do you guys ship to the UK, if so how much are we talking for a motor?.



I can buy either the YX160 or the Z155 bottom end here without too much issue, but to get something along the lines of what I want it seems I have to spend £250 more than I need to and then take parts off and leave/resell them.



Hope that makes sense :D
 

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Any tuner worth a damn should be able to keep that bike well in check with compression ratios up to and including 10:1, especially with EFI. It just takes a little finer tolerance when you get up there. If you can get it anywhere in the 9's Id say your golden. It will also help spool time. I think just a flat top piston should have no trouble dropping you where you need to be, no need to monkey with rods and cranks and jugs.
 

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Discussion Starter #12
I get what you're saying frodo, initally I will be the tuner to get the build running in a tame manner - it will then be handed to a pro to get it all smooth and lovely.



So far I'm thinking of getting this: CLICKY

(Ignore the HP claims - I certainly am ;))



And fitting a steel lined bore as I don't trust the plated/scut stuff yet for this type of project: CLICKY



I plan to pull down the motor and fit Japanese bearings and piston/rings and give it a good fettle.



If anyone can spot any obvious gotcha's please do let me know!
 

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If your not going to use the cylinder or piston anyway..I would save yourself the 400 bucks and just go with a pitster 155HO. I believe the only difference would be the klx vs the honda head, but the klx would give you larger stud spacing and allow for a thicker cylinder at the bores you are considering.
 

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Discussion Starter #14
FrodoGT said:
If your not going to use the cylinder or piston anyway..I would save yourself the 400 bucks and just go with a pitster 155HO. I believe the only difference would be the klx vs the honda head, but the klx would give you larger stud spacing and allow for a thicker cylinder at the bores you are considering.


I checked out the 155HO on TBOLT.com and it looks identical the one on OORacing CLICKY klx ports and all..



About the stud spacing you mention, can you elaborate as I thought he KLX & Honda style heads were interchangable so I'm not getting why you can run a thicker cylinder.



I know I'm probably being a PITA on this, but I'd really like to get it right
 

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the klx style heads have a bigger stud pattern check out T-BOLTS tech section every thing u need to know is in there
 

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On a honda based engine or stud patern you wont get much bigger than a 57mm piston between the studs. On the KLX style heads 66mm piston is now almost common.. Klx stud pattern is MUCH larger than a Honda engine.. Now there use to be some KLX style heads that had Honda ports on it that were on these china engines. YX used them but if its a Honda bottom end you wont get anything bigger than a 57mm piston in there..
 

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Discussion Starter #17
eavery said:
the klx style heads have a bigger stud pattern check out T-BOLTS tech section every thing u need to know is in there


I've been through every page under the tech section, I found this which details the port shape differences: TBolt USA, LLC Tech Database - YX 150/160 ,ZS 155 ,V2 & +R Head types



And this which shows stud spacing, but it's for the 140's or less:



TBolt USA, LLC Tech Database - Engine Info for Kits



So I'm still just as confused lol.



I don't understand how KLX port style heads have a different stud spacing to the Honda style port heads when the only obvious difference is the angle of the ports - :p
 

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The ports are not the key point we are trying to identify with here..you can make either port work just fine with a bit of work but what is being said is that the klx style head has studs which are physically farther apart, meaning that case also has this pattern and that you are able to fit a larger piston in between those studs. If you were to use the pattern that honda uses, then as stated youd be really pushing the limits of the sleeve material by going with a 57mm piston, while the klx headed engines have room to spare well into the 60's..this allows you a bigger bore, and if you had two cylinders of the same bore, one honda, and one klx..then the klx would have more material left over for the sleeve. the 155ho uses a klx style head, and the one you first linked specifically states that it uses a honda style head. I can only assume it is essentially the same engine, with a smaller bore and a much longer stroke to get the displacement it advertizes, with a honda head.



If for some reason their website is wrong, and its a klx..then all your buying is a 155HO with a big bore kit.
 

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MonsterMonkey said:
What I'm trying to achieve is to turbocharge an engine for my Monkey bike.



I have a suitable fuel system, I've gone the Microsquirt ECU route and used some Honda parts for the throttle body, fuel pump etc - I have this mounted and running on a sacrificial engine, I have a wideband 02 sensor setup too - so no nasty carb jetting issues when it comes to tuning.



The Turbo is a Mitsubishi TD-02 sourced from States, originally destined for a Suzuki 660cc car, hence my quest for as many cubes as possible with a reasonably low compression ratio - to get it spinning.



I must stress I am not doing this to make a huge amount of power, more for the actual 'doing of it'


I KNEW IT YAYAYYAYA FOR BOOST, as soon as you said 8.5 to 1 lol. From all the boost articles I have read if you are going to go with a turbo set up you could skip the ECU part and just run a draw through set up instead of a blow through on the carb, but heck if you already have a ECU go with that. I get the concept of just making it work, but if you want to run a reliable set up you should look into the aisin amr300. Very small 300cc supercharger. The only other supercharger that I thought was really cool was the one from powerbikeUSA. I spent 2 years looking for the PowerbikeUSA bolt on kit and then found out they went out of business in 07, and it didnt work sadly, still a really cool set up though




To achieve lower compression since you are running a ECU for fuel, couldnt you just run a nice big flat top piston with a thicker than normal head gasket, and not have to worry about it? Only other option I would consider is possibly is have that nice big flat top piston be forged that way any hot spots that occur the piston will be able to handle it.



Post up some pics of your turbo charger and the bike you plan on putting it on. I love seeing build projects like this. Planetminis needs more of them.
 
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