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Old 01-12-2018, 10:18 PM   #21
spldart
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Nod

Pictures of motor mods please so we can all drool and get the fizzies!



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Old 01-21-2018, 08:36 PM   #22
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[IMG]https://ibb.co/fR6G3b
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Old 01-21-2018, 09:20 PM   #23
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Ok finally got the pics to upload properly... or links anyways. The first pic is the bike itself. There's a pic of my filter setup that I've talked about elsewhere. Just took my k&n out of the box, tossed the box, and epoxied the rubber tube from the carb to the outside of the filter. The zip ties held it in place to dry and I left them for extra strength. There's also a comparison of the 2 different jugs with the original piston and jug on top. Sorry about the crappy photos of the port jobs. Removed all casting marks originally. I went back today and smoothed the intake tube transitions and flattened the curves. The exhaust I rounded the curves as much as possible and opened the the ends to match the new pipes as the old ones had a sort of ramp inside of them that made the inside pipe diameters as the head about 1/2". Now they're about an 1" inside. The head I touched today as well, I trenched the squish areas (as they're dramatically bigger now with a 6mm larger piston) angling them towards the plug and gradually getting deeper and wider towards the chamber. The head was also domed, meaning that the ridges between the combustion chamber and valves, plug, etc were removed and rounded. The areas were left rough to promote better turbulence on intake and compression. There's a pic also of the piston still in the bottom as well as a pic of the new cam about to go in. The jug will be decked another .045 this week before I start putting it back together. As far as how she's been running since the original work.... rich... which is an understatement. I had a lot of carbon to remove from the Head and piston. The the gasket was in great shape, as well as the cylinder wall, rings, piston, rod, and pin. Nothing out of the ordinary when I inspected everything closely. All in all definitely recommend the 300cc swap from China. For $130 I think it was and about 5 hours of time it's a pretty cheap and easy mod if you're mechanically inclined. The other work isn't necessary but doesn't take long and can be done yourself as well... minus the decking unless you have a mill. The cam is the most expensive part and will run you I think they said about $200. You can get titanium springs and retainers for a 95 dr250 for another $200 online If you're inclined. While not required for the cam profile it's added insurance for me with the way I push it. If you do the exhaust openings it will probably cost you a bit to have new pipes made if you can't make those yourself. All in all I paid more for the used and neglected bike than I did for all of the additions combined.
The new shocks, drag bars, sissy bar and brackets, engine mods, sprockets, chain, paint lights... pretty much everything and the bike itself is in the $2,000 to $2200 area. The rich issue is from the starter jet... It's currently a 60 and reguardless of what one may think it effects fuel delivery throughout the rpm range even without choke... and no I don't have choke issues I checked. I'll be dropping that back to a 52.5, changing the pilot from a 17.5 to 20, and main from 147.5 to 150 while taking a couple shims out of the needle. I know that the stock pilot, starter, and a 147.5 main it will run very very lean. The different jets will hopefully correct everything or at least get me in the ballpark. I'll start there and go where it needs from there. When i can afford it I'll dyno tune and run it to get the final numbers.
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Old 01-22-2018, 06:45 PM   #24
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I think I found my oil consumption problem. Part of it I suspect being riding so hard at high rpm's. The other part of it I found is that my breather filter is soaked. It's not dripping, but completely soaked. This tells me that plenty of oil is getting to it and more than likely coming out when I'm in the high rpm's. My theory is that the larger piston is causing extra pressure in the crankcase on the downstroke. This would naturally force more oil into the breather. Right now the breather is attached to the end of the short stock vent hose. I'm going to extend it and mount the breather right under the seat next to the air filter. Hopefully the extra length and elevation will solve it. Otherwise I will have to find other and probably more expensive and extensive solutions. I wonder if a small oil cooler would help eliminate some pressure? A line from the pressure check port to cooler and then to a tap put in the oil filter cover? I'm sure the bike would be thanking me dearly for one anyways with the extra stress on the current setup.
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Old 01-22-2018, 08:34 PM   #25
Water Warrior 2
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Good pics and write-up. Your thread is very educational for any members who are after more performance but don't want a bigger bike. Looking to more updates.
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Old 01-22-2018, 09:25 PM   #26
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That's ultimately what I wanted to achieve... was a cheap bike that could be made to handle more on the cheap. Around here you can pick these bikes up for $1000 and they can modified pretty cheap. I wanted to try and accomplish what others said was impossible for this bike, and show that it can be done for little money. With the 300cc kit itself I was able to easily run a 16t front and 39t rear sprocket and have plenty of torque for 70-75mph and could easily hit 80-82mph for passing. It could peg the needle at 88 but was a little slower climb past 80. This makes the bike very capable for highway speeds and reliability at those speeds. The other mods are probably more than most people's cup of tea but turns the bike into something that can easily keep pace with most 650 and 750cc cruisers. The cam I'm hoping will bring some more torque to the mid and top end to help with passing especially if I have an extra 100lbs or so of rider on the back. The sprockets I'll keep the same as 4th gear now is basically what the stock 5th gear used to be. It allows me to use 5th as basically an overdrive for the highway. The bike is most alive in 3rd and 4th and in those gears feels like I've got twice the motor under me. If anybody has questions I'm more than happy to answer or help if they're interested in building theirs up. The big thing to note for internal parts wise is that the 91-95 Suzuki dr250 is essentially the same size for many parts. The heads are different, the dr250 has more oil journals than the gz that won't match up to your jug. Otherwise it would be nice because half the porting work is already done. Inside the Head though all the rockers, springs, retainers, bearing washer etc etc are same size specs. For these parts there are plenty of aftermarket beefier items you can buy. Unfortunately the bottom end is completely different. The bottom end internals seem to be holding up fine so I don't think anyone needs to worry about rods and the like. That's also with me pushing the bike harder than the average person would. So if 300cc is all someone is wanting to do then I'd suggest that along with Kevlar clutch plates, 16t and 39t sprockets, and the obvious rejetting. One should be able to get all of that for under $300.
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Old Today, 12:58 AM   #27
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Quote:
Originally Posted by kilo0195 View Post
So if 300cc is all someone is wanting to do then I'd suggest that along with Kevlar clutch plates, 16t and 39t sprockets, and the obvious rejetting. One should be able to get all of that for under $300.
I would be willing to bet most riders would really like the extra 20% in displacement and just a 16 tooth sprocket to start. The extra CC's and slightly lower RPM might be very satisfying. The GZ would then have a bit more grunt on long slight uphill grades and into headwinds. My late wife Lynda had that as her only complaint on long trips. New clutch plates would be an obvious option if there was slippage of course.

I may be wrong but I think you are the only rider to actually upgrade a GZ to this level. Your project is fantastic.
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