Performance Ideas

Abramelin · 02-13-2020, 04:49 PM

First off huge thanks to the individuals on here who have worked towards getting more out of their cg250 I picked up a lot from you all so

. This is my first post but I have been lurking for the last 6 months or so, picked up my hawk a few months back and have been planning out mods. Intake mod, vm26 carb, 14t front (not going for top speed) are done. WGK camshaft gets ordered tomorrow after I get paid, when that goes in I will dimple and port the head as well as deck off 1.3mm and maybe a thinner homemade head gasket (running 93 with a booster or going to e85). But it seems, that is about as far as anyone has taken it. Before I continue this rambling let me first say I am not considering costs of part/mods v.s the cost of the bike, or shortening the life of the engine. I am simply contemplating how far this platform can be taken as I cant help myself. First thought is lightened valves, yes this will without a question increase maintenance. But with the ease of work and low cost of parts why not at least discuss it. It seems some have gone hollowed stem (more costly unless you have a capable drill/equipment) while some examples I have seen are dimpled on the rounded portion above where contact on the cylinder head is made (yes this is more so an air movement mod). Next thought lightened flywheel, this seems to be a go to mod for a lot of the other small engine platforms. As there is not one commercially available *yet*. I figure lightening the stock one (outside of areas needed for stator) either through cnc or simply drilling the back area in a proportional manner to ensure balance should create an increase in response. As previously mentioned I am considering switching over to e85 (tested each time for purity, not allowed to sit extended periods of time, carb replaced/rebuilt as needed and up jetted). Power gains on this are as with any NA e85 application, questionable but the cooling effects are not. These engine are clearly loosing efficiency to heat, running e85 would theoretically correct this to an extent and net power just from less energy wasted converting to heat. Also there are several examples of performance gains on small engines from e85 that can be found online. Next is forced induction either the amr300 roots style super charger or the VZ21 turbo, though the supercharger would be easier to tune. The turbo install is several degrees easier than the process of adding a crank pulley, clearancing the amr, pulley alignment, draw through cutout etc etc etc. I would like to also mention I think I have found a company who is producing the 300cc jug and piston for this engine, that was made by (CCW I think) originally but cannot seem to get solid answers as to if it direct fit or requires modification. As I would assume, but google translate only goes so far, yes I know they had heating issues, but if I am running E85 that should be far less of an issue. I look forward to others thoughts and input

Abramelin · 02-13-2020, 05:11 PM

Just to note also on the topic of amr300 v.s VZ21 the VZ21 has premade flanges available to make things a little easier. https://www.amazon.com/Racing-Style-.../dp/B01KZTAJX8

AJboughtamoto · 02-13-2020, 05:13 PM

If your serious about forced induction you may want to reconsider a decked head which will increase compression. Forced induction tends to run better, or at least more reliably with lower compression. The engine has heat soak issues as is, so an oil cooler would be a must imho.

Wild Dog · 02-13-2020, 09:08 PM

Quote:

Originally Posted by AJboughtamoto

If your serious about forced induction you may want to reconsider a decked head which will increase compression. Forced induction tends to run better, or at least more reliably with lower compression. The engine has heat soak issues as is, so an oil cooler would be a must imho.

I guess he would need a dual oil cooler setup. People seem to forget that CG 250 was born as a 125cc engine, that was taken to 230cc.

Its_not_a_honda · 02-13-2020, 10:25 PM

I like your thinking. Idk anything about e85. Sounds like alcohol tho. I do know from my go kart racing days you will need to run the carb dry if it will sit more than a day. Drain the tank if more than a week. It will eat all rubber components and dissolve the aluminum ones. BUT it will run faster.

franque · 02-14-2020, 01:49 AM

Ethanol (the E in E85) is alcohol. I think the 15% gas makes it a little gentler and more forgiving, but basically everything you said is right.

Abramelin · 02-14-2020, 09:17 AM

Quote:

Originally Posted by Wild Dog

I guess he would need a dual oil cooler setup. People seem to forget that CG 250 was born as a 125cc engine, that was taken to 230cc.

Very well aware my dude, given the cooling properties of e85 temps drops about 18% if my memory serves, between that and a singular cooler, temps would probably be lower than the 250 jug stock. But the 300 jug is the last on my list of interests, I only mentioned it as I had read others had an interest in it. But consensus seemed to be it was no longer commercially available.

Abramelin · 02-14-2020, 09:24 AM

Quote:

Originally Posted by AJboughtamoto

If your serious about forced induction you may want to reconsider a decked head which will increase compression. Forced induction tends to run better, or at least more reliably with lower compression. The engine has heat soak issues as is, so an oil cooler would be a must imho.

Thanks for the input, perhaps a lesser deck up to around 9.5.1 ish(1/2mm-1mm?) would be a safer bet, that seems to be a baseline for many forced induction platforms. But from my research it seems some of the turbo e85 race application use upwards of 10.5-11.5.1 but that is in modern application so your point probably still stands.

alex_in_az · 02-14-2020, 06:05 PM

A 300 cc jug would need a bore of 76.6 mm with the same stroke. Can the CG engine cases take that or will they need to be bored out?

Abramelin · 02-14-2020, 07:08 PM

Fairly sure this is the basic process (turn on subtitle if needed both are in Spanish)

Abramelin · 02-14-2020, 07:10 PM

But again the 300cc jug is the least of my interest currently so I could be mistaken.

Wild Dog · 02-14-2020, 09:52 PM

I know my fellow latin americans and trust me, there are a lot of bull going around those 300cc conversion... They are not 300cc, but actually a 250cc conversion.

The base engine is a CG 200 which has a stroke of 62.2 mm now if we add a 72 mm piston we have an engine with a displacement around 253cc... A Far cry from a 300c.
If we use a cg250 which has a stroke of 65 we have an engine that has around 265cc displacement
Yes the cylinder says 300cc but because it was meant to be matched with an engine with a different stroke.

In this area of the world the history goes like this.
Dude without a lot money waste money on a 300cc conversion, tries to race an Honda CBX 250 or even worst a Ktm duke 290, not only they lose because they are outclassed by better engines but they trash their own engine.

Abramelin · 02-15-2020, 10:46 AM

Quote:

Originally Posted by Wild Dog

I know my fellow latin americans and trust me, there are a lot of bull going around those 300cc conversion... They are not 300cc, but actually a 250cc conversion.

The base engine is a CG 200 which has a stroke of 62.2 mm now if we add a 72 mm piston we have an engine with a displacement around 253cc... A Far cry from a 300c.
If we use a cg250 which has a stroke of 65 we have an engine that has around 265cc displacement
Yes the cylinder says 300cc but because it was meant to be matched with an engine with a different stroke.

In this area of the world the history goes like this.
Dude without a lot money waste money on a 300cc conversion, tries to race an Honda CBX 250 or even worst a Ktm duke 290, not only they lose because they are outclassed by better engines but they trash their own engine.

Thank you for the info I hadn't put pen to paper but that makes sense

Weldangrind · 02-16-2020, 07:44 PM

Welcome, Abramelin! Whatever you decide, I'll certainly be following. I've had hillbilly ideas of supercharging with a smog pump, but as you say, the drive pulley presents a challenge. I'm pretty sure that it would be easy to mill a hole in the stator cover and fit it with a seal, but the connection of a shaft to the flywheel / crank makes my mind into a pretzel. I had a nap instead.

A turbo presents challenges as well, but none of them insurmountable. I bought a book on it and it'll be my next read; the prelim info points to pressurizing the bowl through the vent to compensate for increased air velocity and volume. Sounds easy enough. I'm a neophyte when it comes to turbos, but I've learned that a blow-through setup is preferred, to prevent puddling in the turbo and plumbing. Sounds logical.

Wringing out a CG with forced induction makes me giggle. As you pointed out, the cost of ownership and repair (even after catastrophic carnage) is quite affordable. Seriously, skip going out for coffee and use that cash for parts.

If I had decent access to e85, I'd be all over it. I read quite a bit about it when it first hit the market, and I love the idea of gov't subsidized race fuel. The average seems to run between 105-110 octane, which would certainly help thwart detonation (combustion chamber inefficiencies aside).

Abramelin · 02-28-2020, 10:46 PM

Head is off and disassembled, .01mm head gasket made will probably end up around .02-.03 with a little rtv. Intake manifold and my vm26 have been ported/matched and dimpled. Head is will get the same in the A.M. Will be lightening valves by evenly sanding material in the center of the stem above where the seals are made and below where the retainers go. Will weigh difference between before and after. Trying to find someone in my area to weld my exhaust after I cut the cat out as I don't want to go by a welder for that alone. Carb jets were hand drilled somewhere in the realm of e85 (hopefully) will almost def need to adjust as I kind of just "eyed" it lol. Cam hasn't been ordered yet, my schedule has been all over the place and I have been sick for the last 3 weeks. Next stage will be cam and lightening the flywheel.

02-13-2020, 04:49 PM	#1
Abramelin Join Date: Jan 2020 Location: South Texas Posts: 15	Performance Ideas First off huge thanks to the individuals on here who have worked towards getting more out of their cg250 I picked up a lot from you all so . This is my first post but I have been lurking for the last 6 months or so, picked up my hawk a few months back and have been planning out mods. Intake mod, vm26 carb, 14t front (not going for top speed) are done. WGK camshaft gets ordered tomorrow after I get paid, when that goes in I will dimple and port the head as well as deck off 1.3mm and maybe a thinner homemade head gasket (running 93 with a booster or going to e85). But it seems, that is about as far as anyone has taken it. Before I continue this rambling let me first say I am not considering costs of part/mods v.s the cost of the bike, or shortening the life of the engine. I am simply contemplating how far this platform can be taken as I cant help myself. First thought is lightened valves, yes this will without a question increase maintenance. But with the ease of work and low cost of parts why not at least discuss it. It seems some have gone hollowed stem (more costly unless you have a capable drill/equipment) while some examples I have seen are dimpled on the rounded portion above where contact on the cylinder head is made (yes this is more so an air movement mod). Next thought lightened flywheel, this seems to be a go to mod for a lot of the other small engine platforms. As there is not one commercially available yet. I figure lightening the stock one (outside of areas needed for stator) either through cnc or simply drilling the back area in a proportional manner to ensure balance should create an increase in response. As previously mentioned I am considering switching over to e85 (tested each time for purity, not allowed to sit extended periods of time, carb replaced/rebuilt as needed and up jetted). Power gains on this are as with any NA e85 application, questionable but the cooling effects are not. These engine are clearly loosing efficiency to heat, running e85 would theoretically correct this to an extent and net power just from less energy wasted converting to heat. Also there are several examples of performance gains on small engines from e85 that can be found online. Next is forced induction either the amr300 roots style super charger or the VZ21 turbo, though the supercharger would be easier to tune. The turbo install is several degrees easier than the process of adding a crank pulley, clearancing the amr, pulley alignment, draw through cutout etc etc etc. I would like to also mention I think I have found a company who is producing the 300cc jug and piston for this engine, that was made by (CCW I think) originally but cannot seem to get solid answers as to if it direct fit or requires modification. As I would assume, but google translate only goes so far, yes I know they had heating issues, but if I am running E85 that should be far less of an issue. I look forward to others thoughts and input
	1

02-13-2020, 05:13 PM	#3
AJboughtamoto Join Date: Mar 2018 Posts: 123	If your serious about forced induction you may want to reconsider a decked head which will increase compression. Forced induction tends to run better, or at least more reliably with lower compression. The engine has heat soak issues as is, so an oil cooler would be a must imho. __________________ 2019 Brozz 250 1999 Gas Gas EC300 2003 ZX6R 1991 Voyager XII
	3

02-13-2020, 10:25 PM	#5
Its_not_a_honda Join Date: Jan 2018 Posts: 410	I like your thinking. Idk anything about e85. Sounds like alcohol tho. I do know from my go kart racing days you will need to run the carb dry if it will sit more than a day. Drain the tank if more than a week. It will eat all rubber components and dissolve the aluminum ones. BUT it will run faster. __________________ 2020 Kawasaki KLX300R, 2018 Yamaha TW200 If you want more of something, tax it less. If you want less of something, tax it more.
	1

02-14-2020, 06:05 PM	#9
alex_in_az Join Date: Aug 2013 Location: Goodyear, Arizona Posts: 407	A 300 cc jug would need a bore of 76.6 mm with the same stroke. Can the CG engine cases take that or will they need to be bored out? __________________ 2020 Tao TBR7 9.3:1 PnP head CRF230F exhaust 4 degree advance key 290 degree cam Nibbi PE30 and cone filter Front fork brace
	0

02-16-2020, 07:44 PM	#14
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Welcome, Abramelin! Whatever you decide, I'll certainly be following. I've had hillbilly ideas of supercharging with a smog pump, but as you say, the drive pulley presents a challenge. I'm pretty sure that it would be easy to mill a hole in the stator cover and fit it with a seal, but the connection of a shaft to the flywheel / crank makes my mind into a pretzel. I had a nap instead. A turbo presents challenges as well, but none of them insurmountable. I bought a book on it and it'll be my next read; the prelim info points to pressurizing the bowl through the vent to compensate for increased air velocity and volume. Sounds easy enough. I'm a neophyte when it comes to turbos, but I've learned that a blow-through setup is preferred, to prevent puddling in the turbo and plumbing. Sounds logical. Wringing out a CG with forced induction makes me giggle. As you pointed out, the cost of ownership and repair (even after catastrophic carnage) is quite affordable. Seriously, skip going out for coffee and use that cash for parts. If I had decent access to e85, I'd be all over it. I read quite a bit about it when it first hit the market, and I love the idea of gov't subsidized race fuel. The average seems to run between 105-110 octane, which would certainly help thwart detonation (combustion chamber inefficiencies aside). __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	1

02-13-2020, 05:11 PM	#2
Abramelin Join Date: Jan 2020 Location: South Texas Posts: 15	Just to note also on the topic of amr300 v.s VZ21 the VZ21 has premade flanges available to make things a little easier. https://www.amazon.com/Racing-Style-.../dp/B01KZTAJX8
	0

02-14-2020, 01:49 AM	#6
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	Ethanol (the E in E85) is alcohol. I think the 15% gas makes it a little gentler and more forgiving, but basically everything you said is right.
	1

02-14-2020, 07:08 PM	#10
Abramelin Join Date: Jan 2020 Location: South Texas Posts: 15	Fairly sure this is the basic process (turn on subtitle if needed both are in Spanish)
	0

02-14-2020, 07:10 PM	#11
Abramelin Join Date: Jan 2020 Location: South Texas Posts: 15	But again the 300cc jug is the least of my interest currently so I could be mistaken.
	0

02-14-2020, 09:52 PM	#12
Wild Dog Join Date: Dec 2016 Location: Argentina Posts: 756	I know my fellow latin americans and trust me, there are a lot of bull going around those 300cc conversion... They are not 300cc, but actually a 250cc conversion. The base engine is a CG 200 which has a stroke of 62.2 mm now if we add a 72 mm piston we have an engine with a displacement around 253cc... A Far cry from a 300c. If we use a cg250 which has a stroke of 65 we have an engine that has around 265cc displacement Yes the cylinder says 300cc but because it was meant to be matched with an engine with a different stroke. In this area of the world the history goes like this. Dude without a lot money waste money on a 300cc conversion, tries to race an Honda CBX 250 or even worst a Ktm duke 290, not only they lose because they are outclassed by better engines but they trash their own engine.
	1

02-28-2020, 10:46 PM	#15
Abramelin Join Date: Jan 2020 Location: South Texas Posts: 15	Head is off and disassembled, .01mm head gasket made will probably end up around .02-.03 with a little rtv. Intake manifold and my vm26 have been ported/matched and dimpled. Head is will get the same in the A.M. Will be lightening valves by evenly sanding material in the center of the stem above where the seals are made and below where the retainers go. Will weigh difference between before and after. Trying to find someone in my area to weld my exhaust after I cut the cat out as I don't want to go by a welder for that alone. Carb jets were hand drilled somewhere in the realm of e85 (hopefully) will almost def need to adjust as I kind of just "eyed" it lol. Cam hasn't been ordered yet, my schedule has been all over the place and I have been sick for the last 3 weeks. Next stage will be cam and lightening the flywheel.
	0