01-28-2018, 01:28 AM | #16 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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It was my pleasure guys. Just remember that my explanation is pretty simplified, but if you do a little google searching you can come up with all sorts of information that will go more in depth than I did. If you really want to get into tuning, you can always install a wideband O2 on the exhaust to really aid in dialing in carb tuning. Kind of an expensive route to go, but it can always be used on other bikes in the future. Simply put a plug in the sensor bung when not in use. The old fashioned way is to read the spark plug. You can find a charts like this one to help point you in the right direction. http://bustekhub.com/wp-content/uplo...on-Chart-1.png Really, once you start messing with carb tuning you realize how simple it really is. The only other thing to really keep in mind is that since these carbs are purely mechanical in nature, if the air density altitude changes via temp swings or large enough elevation changes, the bike will run leaner or richer. The general rule of thumb with Mikuni jetting is a full jet size per 5000ft altitude or 50 degree change in temp. Aka, you have a 115 main jet that is perfect in 90 degree temps, once the air temp drops below 40 degrees it is a good idea to step up a jet size to a 120, or at least half a step like a 117.5
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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02-14-2018, 01:08 AM | #17 | |
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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Dan I bought the Mikuni Carb after talking with Sean. His bike ran great, and his idle/acceloration improved a lot. He used a 27.5 pilot, and a 115 main, and did not make any needle adjustments. Bike ran/started perfect. He is at about 800ft, and it was about 45-60 degrees. I am at about 60-200 ft where I'll be riding the bike, and the temp will be about 50-100 degrees (right now were around 50-60 deg) (Summer will be around 90-105). should I start with the same 30/115, or should I start with a 30/117.5? Currently I have it jetted at 30/117.5, but I have 27.5, 25, 112.5, 115, & 120 jets if needed. I am planning on installing it this weekend. Last edited by Douglass; 03-05-2018 at 03:00 PM. |
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02-14-2018, 12:28 PM | #18 | |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Quote:
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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02-14-2018, 01:26 PM | #19 | |
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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02-25-2018, 06:39 PM | #20 |
Join Date: Jan 2018
Posts: 410
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shocks
I know I've read a thread about a guy putting a Honda shock on one of these. I was just wondering around looking at parts and ran across this shock. https://www.gvabrands.com/parts-acce...x37/rear-shock . It is for an apollo 250 water cooled bike. I am wanting to try it out but don't know if it will clear on a DB38 apollo 250. It has a reservoir off to one side. My shock is a little stiff for my needs and I thought this might be a bolt in. It would really beat welding and fabricating a new air box.
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04-07-2018, 07:31 PM | #21 |
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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So I was starting to have some idle issues with the bike, and it would not stay running at idle, so I decided it was time to change the carb out to the Mikuni. I am at sea level, and decieded to start with the 30 pilot, and 120 main jet. The air screw came preset at 2 1/2 turns out, and I left it at that to start with. The bike started right up with the choke on, and ran perfect once the choke was turned off. The bike idles soooo much better. No driveability issues at all, idle, very light throttle, heavy throttle, and WOT throttle were spot on. All I had to do is just make a very small adjustment to the idle.
One thing to note was the cap on the top of the stock carb were the throttle cable goes through was loose, and not seated. This could have been causing some of the issues, but I had already taken everything apart so Installed the new Mikuni carb anyway. You will need to remove the plastics, seat, gas tank, loosen the two nuts holding the carb to the intake manifold, air box clamp, pull the carb towards the air box, and push it down, remove the upper intake manifold bolt, loosen the lower intake manifold bolt, swing the intake manifold out of the way, and remove the original carb, and install the new one. Then assemble everything back together. I was also able to reuse the stock throttle cable with no modifications. There where also no cleance issues with the new carb. Great upgrade. Next project will be to take the bowl off the stock carb to see how it was set form the factory. |
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04-07-2018, 08:56 PM | #22 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Now you see why so many of us just switch to the Mikuni. It isn't really necessary, but it makes dialing in the bike so much easier. Specifically thanks to all of the other people that have been running them. Lots of examples to kind of get a baseline setup for.
I am rather impressed that the 30 pilot takes 2 1/2 turns to idle on your bike. My bike would barely idle at 1 1/2 turns on a 30 pilot, and I ended up below 1 turn out to get a smooth stable idle. That is why I dropped to the 27.5
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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04-08-2018, 10:11 AM | #23 | |
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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Also, I read your right up a few times to get a better understanding on how each jet, and needle role. Thank you for your help! |
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04-10-2018, 04:45 AM | #24 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Glad to help. So many people view carb tuning as some sort of black magic thing, but in reality it is all rather simple. Understanding each jets role at given throttle positions and getting a feel for how an engine sounds and behaves when too rich or lean is 90 percent of it.
The HARD thing to do is tune a carb from scratch. I am not looking forward to setting up my VM30 when I get around to it.
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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04-10-2018, 11:18 AM | #25 | |
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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Here is the finished pictures of the bike. I installed the Tusk Racing CV high bars, 52T rear sprocket, new 530 unibear o ring chain, Pro taper gripps, and the Mikuni 30mm Carb. |
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04-11-2018, 07:00 AM | #26 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Love the bars. The Renthal fat bars I put on my Hawk made a huge difference in feel and looks. I love them.
It's a sweet looking bike, and that rear sprocket is huge lol. Honestly, if they would have sold the Dual sport version of that bike here in the States, I would have bought it. I love these bikes.
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Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124 |
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04-12-2018, 11:40 AM | #27 | ||
Join Date: Aug 2017
Location: Bay Area, CA
Posts: 375
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