Motor Upgrades - 88cc/106cc what to expect

Darrie · Aug 7, 2014

I love this chart from Minimob racing.... Whilst it's for a CRF50 motor, it does however drive home what to expect when adding performance mods. I'm presuming they remove the rev limiter after the new head is installed to take advantage of the higher RPM.

50cc std - bottom graph line of course !
88cc std exhaust & carb - double the output above std in all the rev range. (Blue)
88 +new head, pipe & carb - top end starts to rev out more and produces solid power at higher engine revs. (Green)
88 +new head, pipe, carb & Cam - very slight bottom end loss, but mid - top end more power. (Orange)
106 (Red & purple) same as last 2 above but with the extra 18 cubes.

Some things we can learn from this chart
- If you are a rev head, buy a race head as you will be reving more, changing less and getting more power. Smart move given these bikes generally have 3 gears only. Noise will be the main downside, and I see why people clearly recommend race heads when buying an 88cc kit.
- All the bells and whistles do little more in the early to mid rev range that the 88cc kit alone delivers.
- judging by the power curve don't bother adding a rev box if you don't have a race head as the power is falling off anyway
- Bang for buck the 88cc kits are pretty good at simply turning the power up !

In case they ever take it down off the site ...

sh0rtlife · Aug 7, 2014

ive been wondering exact how much each one does..id LOVE to see the aftermarket numbers tossed in for comparison...lifan, piranaha etc

but this right here pretty much has me sold on just doing 88's and being happy

storminnorman07 · Aug 7, 2014

Darrie said:
I love this chart from Minimob racing.... Whilst it's for a CRF50 motor, it does however drive home what to expect when adding performance mods. I'm presuming they remove the rev limiter after the new head is installed to take advantage of the higher RPM.

50cc std - bottom graph line of course !
88cc std exhaust & carb - double the output above std in all the rev range. (Blue)
88 +new head, pipe & carb - top end starts to rev out more and produces solid power at higher engine revs. (Green)
88 +new head, pipe, carb & Cam - very slight bottom end loss, but mid - top end more power. (Orange)
106 (Red & purple) same as last 2 above but with the extra 18 cubes.

Some things we can learn from this chart
- If you are a rev head, buy a race head as you will be reving more, changing less and getting more power. Smart move given these bikes generally have 3 gears only. Noise will be the main downside, and I see why people clearly recommend race heads when buying an 88cc kit.
- All the bells and whistles do little more in the early to mid rev range that the 88cc kit alone delivers.
- judging by the power curve don't bother adding a rev box if you don't have a race head as the power is falling off anyway
- Bang for buck the 88cc kits are pretty good at simply turning the power up !

In case they ever take it down off the site ...
View attachment 146420

take takegwas numbers then take about a 3rd off the max hp value and thats about what you'll see on a dynojet in the states

Darrie · Aug 8, 2014

storminnorman07 said:
take takegwas numbers then take about a 3rd off the max hp value and thats about what you'll see on a dynojet in the states

LOL true, and what product manufacturer wouldn't show optimum results.

And of course they don't overstate the standard power curve (at 2-2.5 hp) as it helps keeps the the distance in between lines, but hey its pretty self explanatory as to what happens with these options.

My thoughts are I'm not after a race motor on the Z50R ... but I'm thinking along the lines after the 88cc kit/jet upgrade I may look at the cheaper options that do allow it to rev a bit better. That may involve a cam/revbox that are relatively cheap. Interested to see if I could simply improve the upper revs power curve so it doesn't drop off so significantly without tampering with the exhaust or outlaying for a race head.

storminnorman07 · Aug 8, 2014

Darrie said:
LOL true, and what product manufacturer wouldn't show optimum results.

And of course they don't overstate the standard power curve (at 2-2.5 hp) as it helps keeps the the distance in between lines, but hey its pretty self explanatory as to what happens with these options.

My thoughts are I'm not after a race motor on the Z50R ... but I'm thinking along the lines after the 88cc kit/jet upgrade I may look at the cheaper options that do allow it to rev a bit better. That may involve a cam/revbox that are relatively cheap. Interested to see if I could simply improve the upper revs power curve so it doesn't drop off so significantly without tampering with the exhaust or outlaying for a race head.

http://www.hondatrailbikes.com/catalog/product_info.php?cPath=52_53&products_id=710 IMHO opinion dollar vs hp gained this is a guys/gals best bang for the buck.

Darrie · Aug 8, 2014

See where you are going ...the green line on the graph.

I'm trying to keep both induction and exhaust noise down (highly improbable I know). The difference between the XR50 and Z50 is enough for me to think long and hard about exhausts. As OEM exhausts seem to be the best at keeping the noise down I'm looking at higher CC donor bike mufflers from the bike recycling yards.

sh0rtlife · Aug 8, 2014

thats not a bad idea...my big gun is just under the "too loud" point for me...its still quieter than my xr's so im pleased..tho i wish it was a smidge quieter..but some of that could be a need of a re-pack...something else to consider from "bigger CC" engines would be say 200cc quads..better flow low decible....god knows my 200sx fourtrax is pretty silent and the pipe isnt all that big atleast compared to my xl600r

Darrie · Aug 8, 2014

Dont laugh, but this is the muffler I'm considering on my sons Z50R... I've seen them as low as $50 new

nielspbr · Aug 8, 2014

Aint that "thing" a bit heavy?

(as you aree using a monoshock you have more room. I think you do not even have to try that muffler with stereo shocks.)
As an alternative you can try a muffler of a 125cc pbr.

T Bolt USA · Aug 9, 2014

Im going to have to agree with storminnorman07 on this one

Best bang for the buck
You can add a 108cc stroker for $150
[h=1]TB Race Head, 88cc Big Bore & 20mm Carb Kit
Z50 CRF50 XR50 CRF70 & Pit bikes
Part No: TBW0936
Location: 220C[/h]

Z50 CRF50 XR50 CRF70 & Pit bikes1" width="250" height="208" zc="1" hspace="5" vspace="5" title=".TB Race Head, 88cc Big Bore & 20mm Carb Kit
Z50 CRF50 XR50 CRF70 & Pit bikes" style="border: 0px; -webkit-box-shadow: rgb(0, 0, 0) 0px 0px 1px;">
SPECIAL
includes Oil Pump, CDI, Main Jet Kit, and Clutch Cover Gasket for the same price as our regular kit
Trail Bikes Race Head, 88cc Bore & 20mm Carb Kit

This is the Race Head 88 kit that everyone is talking about

Performance and Price make Mike's Honda Trail Bike 88 w Race head a real winner

Race Head, 88cc Big Bore kit, and 20mm Carburetor Performance Kit:

- Lightweight aluminum cylinder with steel sleeve

- Cast in mounts on cylinder for aftermarket skid plates

- Oversized cooling fins on cylinder for efficient heat dissipation

- 52mm piston with rings, pin, & clips

- Head gasket kit

- High performance race camshaft

- Race Head – Larger valves (25mm intake & 22mm exh) and porting for increased performance. Also has bigger cooling fins. Includes all necessary parts. Comes disassembled.

- 20mm Performance carb assembly. Includes: 20mm carb, intake, heatstop, gaskets, mounting hardware/wrench, air filter (not shown in pic) and long throttle cable

Installation Note: It will save a lot of time and effort if the oil pump is installed while installing the bore kit (requires cylinder removal).

See the Performance Info section for additional information on our performance parts.
works with
Z50-XR50-CRF50 92-Present
all XR70 & CRF70
China 50cc and 70cc

Darrie · Aug 9, 2014

T Bolt USA said:
Im going to have to agree with storminnorman07 on this one

Best bang for the buck

No arguement here that TB is the way to go. 106 kit hell yes that will get it moving.

However I'm 54, and despite my wife telling me I'm going deaf I'm over loud exhausts. I want to be able to sneak around on the bike in quiet mode.. even creep up on the odd duck as I like it as a trail bike. I want it to sound like a fifty Z (the sound of nothing LOL)

Seriously though, I know its not the norm, but give me a heads up on what you think the outcome might be with the full TB kit and the standard exhaust ? Have you guys at TB ever done this and succeeded in keeping it quiet ?

My thoughts are maybe that a nice bigger flow OEM exhaust say off a gromet 125 may help so that these type of upgrades are not as restricted as the Z50 pipe. The gromets being an EFI high revving 125 its exhaust must be able to deal with more flow.

nielspbr · Aug 9, 2014

Do not forget that the inlet will get louder too. (in fact the carb suction and the chain make the most noise on my Z)

storminnorman07 · Aug 9, 2014

Darrie said:
No arguement here that TB is the way to go. 106 kit hell yes that will get it moving.

However I'm 54, and despite my wife telling me I'm going deaf I'm over loud exhausts. I want to be able to sneak around on the bike in quiet mode.. even creep up on the odd duck as I like it as a trail bike. I want it to sound like a fifty Z (the sound of nothing LOL)

Seriously though, I know its not the norm, but give me a heads up on what you think the outcome might be with the full TB kit and the standard exhaust ? Have you guys at TB ever done this and succeeded in keeping it quiet ?

My thoughts are maybe that a nice bigger flow OEM exhaust say off a gromet 125 may help so that these type of upgrades are not as restricted as the Z50 pipe. The gromets being an EFI high revving 125 its exhaust must be able to deal with more flow.

You know you can run the 108cc TB kit with the factory exhaust right? This will keep Db levels down. The engine will naturally have a little more growl but it won't be abnoxiously loud. Just keep in mind with the use of the factory exhaust the kit will not yield it's full horsepower potential.

Darrie · Aug 10, 2014

nielspbr said:
Do not forget that the inlet will get louder too. (in fact the carb suction and the chain make the most noise on my Z)

Thanks for the inlet noise reminder and also the weight reminder on an OEM exhaust. I swear every time I take the exhaust of my XR600 that I have to replace it with something lighter .. its like a ship anchor, but I suppose thats how it keeps the bike so quiet.

Secret is I think finding an exhuast from a street model that is a registerable bike .. like XR125, grom etc. If I wasn't going for a boat anchor exhaust the Yoshimura grom exhaust would be the ticket ...but the moment they say they are not street legal says it all.

Can't see many PBR125 exhausts for sale. I'm also going to check out baffle options also...maybe an option for reinserting a slightly larger baffle and exit pipe. I'm also really liking the arrow brand of aftermarket exhausts.

sh0rtlife · Aug 10, 2014

yeah that boat ancor xr exhaust is the same boat ancor on my XL600......and its entirely how its baffled...

if i was going for full silence..i would find a stock 50 exhaust i could get for cheep..even if its mangled or rusted out...toss it on the bandsaw and cut it open...then re-create the ssame setup with bigger in/out opening up all of the chambers a bit..in theory you could make a very good flow while keeping it quiet...

the other option would be looking at late 70s and early 80s xl125/200 maybe even the 250s but ONLY the XL models as they would be the quiet versions

Motor Upgrades - 88cc/106cc what to expect

Darrie

sh0rtlife

storminnorman07

Darrie

storminnorman07

Darrie

sh0rtlife

Darrie

nielspbr

T Bolt USA

Darrie

nielspbr

storminnorman07

Darrie

sh0rtlife

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