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G1 engine mods and custom exhaust systems

G1 engine mods and custom exhaust systems

Postby Wallingford Racing » Wed May 10, 2006 10:03 pm

We have just recently discovered the G1 engines are very much like the specialty racing engines we build for many winning Yamaha vintage snowmobile racers.We have decided to build some pump gas high performance engines for use in stock or close to stock chassis. We will finish up on Friday and will do some testing if the rain holds out. We will dyno the engine and exhaust package to verify our predictions but we are suspecting at least 30 hp. The engine has extensive porting and head work. The carb was replaced with a taper bored 30mm Mikuni and the exhaust pipe is tuned for a little higher rpm so extra speed will come naturally. The pipe has a quiet muffler so noise will not be a problem and the pipe fits in the stock location. Stock cables for carb and choke are retained. We do however suggest premixing the fuel and oil and the ratio needs to be at least 60:1 along with running the stock oil injection system. We would suggest near a 32:1 premix if no oil pump is used.
If anybody has any input on these G1 carts and their weaknesses or high performance parts needed we would like to here about it. We are new to the golf cart world and happen to find this forum because we ordered our rebuild parts from Buggies Unlimited.
If all works out maybe B.U. would like to carry some of our performance parts for G1's. I will post pics of the finished G1 hopefully next week.
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Postby 1981G1 » Wed May 10, 2006 11:09 pm

I'd be interested to hear more about the mods on your motors. I've calculated that this motor is good for 8000 rpm reliably, and you could squeak it to 10,000 rpm periodically. What have you found as far as safe rpm? The key issue with this motor is air flow(as with any 2-stroke). From the factory, it is unbelievably restricted and the porting leaves nothing to be desired. I've done some minor work to the head, intake, transfer ports and port matched the exhaust, with remarkable improvements over stock. Running a B-type 34mm mikuni carb(for experimenting), and still playing with the jetting. It is working very well right now, but still looking for more power. I don't have access to a dyno, but would venture to say that the power has more than doubled. I suspected that these motors could produce at least 20hp, and I hope to see your test results soon. Keep us informed.
As far as the weaknesses on the G1, be careful with the motor mounts if you're going with that much power. I am going to install a limiter strap on my motor. Also, take a look at the starter/generator if you plan on increasing the motor rpm.
COTM SEPT '06 -- 1981 G1, 4" Homemade lift, 22x11x8 tires, Custom Front Cowl. Digital speedometer. 100w AM/FM/CD. 32+mph. Looking for more power. SOLD
1989 EZGO Marathon -- 4" Homemade lift, Camo paint, 23x7x10 front, 22x11x10 rear
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Postby Wallingford Racing » Wed May 10, 2006 11:50 pm

We work quite a bit with these Yamaha single cylinder F/C engines. We normally run them in the winter so heat is not an issue then. I don't want it to be a hot running engine if we cam avoid it but running it in 100 deg weather has to be tough to keep it cool.
As for the rpm we are keeping it in the 7000 rpm range. I'm not even sure what rpm a bypassed govenor set up would achieve? Any idea?
These engines are only 215cc, so 30 hp is about it on pump gas and keeping the low end power still there. Clutch engagement should be around 4000 rpm but we need to make sure it doesn't break stuff with the low engagement first.
We are the leading engine and pipe builder for guys running the Yamaha single cylinder vintage sled engines. They are 292cc singles and produce 25-29 hp from the factory. When we are done with them they produce up to 55 hp at 7900 rpm. These engines can easily be made to bolt into these carts. The 292's are just a little larger than these G1's and the clutch would bolt right on.
The stock G1 cylinder needs major mods to breathe enough to produce over 30 hp, but may only need a pipe and carb to produce 20 hp. What sort of hp rating is on the stock engine? What rpm?
I also would not suggest anything over 30mm carb so as to keep the tuning easy. We are using a 30mm that is taper bored to 34mm and we made a simple adapter plate to bolt the new carb adapter to.
The cylinder base also needs to be machined a lot (.040") to achieve a 0mm deck. The original head gasket measured .045" thick, which is what the installed squish gap should be (stock measured .085"). We also machined the head quite a bit but the porting was very extensive so the head needed to be cut quite a bit as well. I would say the G1 could handle some higher rpm (9000 plus) but when you do this the clutching becomes very critical and the low rpm running suffers. Today we fired the engine (without the pipe) and it crackled to life perfectly and seemed to have good low end power. Friday we will find out.
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Postby clutch33 » Thu May 11, 2006 2:36 pm

Sweet 8) 8) Can't wait
Second place is just the 1st looser
1984 G-1 homemade 4"lift
Brite Diamond plate:floor,sides rails,dash
20x11x10's bling bling wheel covers
coming soon 6"lift,stereo,chop top,chop windshield,kick panel & diamond mat footrest
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Postby Wallingford Racing » Thu May 11, 2006 8:09 pm

We took a picture today of the pipe all tacked up and ready to weld. I can't figure out how to post them directly. Can I do that or do I need to put them on a web page first then link to it?[/img]
Wallingford Racing
 
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Postby 1981G1 » Thu May 11, 2006 9:27 pm

You need a web host to transfer the pics to, then link them on this forum.
COTM SEPT '06 -- 1981 G1, 4" Homemade lift, 22x11x8 tires, Custom Front Cowl. Digital speedometer. 100w AM/FM/CD. 32+mph. Looking for more power. SOLD
1989 EZGO Marathon -- 4" Homemade lift, Camo paint, 23x7x10 front, 22x11x10 rear
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Postby Wallingford Racing » Fri May 12, 2006 9:06 pm

We ran it today and it runs well. We hooked up a tach to check what the engagement was and the shift rpm. It engages the clutch at 3000 and shifts at 6500 rpm. We are going to set up the radar gun and check speed. I think 40 mph would be a good safe speed to shoot for. We are using the stock clutches with stock springs and just grinding weight off the arms in the drive clutch to achieve the rpm desired. The new exhaust has a little more noise but is not loud at all. With a little more time on it and some carb jetting we should be in good shape. I think @ less than $1000 it's a great bang for your buck, especially if your rebuilding the engine anyway.
Wallingford Racing
 
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Postby Wallingford Racing » Fri May 12, 2006 9:58 pm

Image
Hopefully this link works.[/img]
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Postby kenaroo » Sat May 13, 2006 7:04 pm

I'd be interested in one of your pipes... I had a kt100 carting pipe on mine but it made the power band way off.. it had no bottom.

I would be interested in your cylinder and head mods as well.

I blew out the rod bearing last month and have ordered the parts and bearings, seals and gaskets. (going .80 over on the piston)

shoot me a pm with your contact info to discuss.
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g1 mods

Postby mnjettr » Mon Mar 12, 2007 2:57 pm

I came across this topic and it seemed to just fizzle out?? I want to mod my yamaha G1. I was told a yamaha 250 bravo snowmobile top end would bolt up?? I have one of these engines (250) has anyone done this?? or looking for any other mods being done to the mighty G1...
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G1 mods

Postby mnjettr » Tue Mar 13, 2007 9:00 pm

my snowmobile engine has a 70mm bore and 64mm stroke. I can't find bore and stroke for the G1, can anyone help me out??? thanks
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Postby 1981G1 » Tue Mar 13, 2007 9:07 pm

215cc
68mm x 59mm
COTM SEPT '06 -- 1981 G1, 4" Homemade lift, 22x11x8 tires, Custom Front Cowl. Digital speedometer. 100w AM/FM/CD. 32+mph. Looking for more power. SOLD
1989 EZGO Marathon -- 4" Homemade lift, Camo paint, 23x7x10 front, 22x11x10 rear
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Postby mnjettr » Tue Mar 13, 2007 9:47 pm

[quote="1981G1"]215cc
68mm x 59mm[/quote
thanks 81g1, that shoots the top end swap in the ars.(wrong stroke) I have a 250 enticer engine thats 73X59?? hmmmmm now that could work.
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Postby 1981G1 » Tue Mar 13, 2007 9:52 pm

Is the enticer motor a single cylinder? If it is, why not swap the whole motor out. A 250 Bravo motor is a good swap candidate.
COTM SEPT '06 -- 1981 G1, 4" Homemade lift, 22x11x8 tires, Custom Front Cowl. Digital speedometer. 100w AM/FM/CD. 32+mph. Looking for more power. SOLD
1989 EZGO Marathon -- 4" Homemade lift, Camo paint, 23x7x10 front, 22x11x10 rear
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Postby mnjettr » Wed Mar 14, 2007 10:03 am

1981G1 wrote:Is the enticer motor a single cylinder? If it is, why not swap the whole motor out. A 250 Bravo motor is a good swap candidate.

both the enticer and bravo are singles. (piston port)was thinking a top end swap would be easy and keep all the the electrics stock for the cart. do you think a 73mm cyl. would bolt up to the g1 bottom?? I may buy a base gasket for the g1 before I start my project to see if its a match to the 250
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