03-09-2021, 11:10 AM | #1 |
Join Date: Nov 2020
Posts: 21
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Same noob, new questions ...
First of all, thanks to all of you for setting this up and somehow making and maintaining a helpful and non toxic community. (Gets more rare online everyday)
Secondly, learned the other day these bikes can wheelie, I make the world's least elegant flag, and since I somehow saved it and didn't die. I hope everyone gets thier seven chuckles out of it (I did, after I changed pants .... lol) QUESTION: Brozz recon with 250 miles Changed my oil today from the shipped stuff, to Rotella T4 15-40W. I've now noticed a stutter at WOT with a 5 to 7 MPH drop at top speed. I plan on checking the valve clearance again after work (my engines warm ..... .. riding RULES) Is there anything else you guys can think of i should look at? Post got cut off the first time, sorry Last edited by Oldwolf; 03-09-2021 at 12:12 PM. |
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03-09-2021, 12:15 PM | #2 |
Join Date: Jan 2020
Posts: 287
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Check the valve clearance on a cold engine!
I experienced the same issue with top speed drop with my Brozz after changing out the break in oil and adjusting the valves.
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2019 Z 400 2020 Tan Recon 2021 KLX 300 2022 GPX FSE 450R |
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03-09-2021, 02:24 PM | #3 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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What did you set the valve lash to, out of curiosity?
As far as the stutter at WOT, and a drop in speed, generally I would say that is related to main jet sizing. If you have any jets on hand, I would start there. I find it interesting that right at the mile point where our Hawks tend to free up and actually gain a little top end you guys are losing 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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03-09-2021, 04:08 PM | #4 |
Join Date: Nov 2020
Posts: 21
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I'm away from my owners manual at the moment, but I think the book says .005.
As far as jets go, the stutter is new since the oil change. I don't mind changing jets, but is the 15-40 enough thicker I should need more fuel? If so, what can I use till I can get new jets? |
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03-09-2021, 05:27 PM | #5 |
Join Date: Oct 2020
Location: Flower Mound Texas
Posts: 904
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Check your spark plug. The stockers are known th have issues.
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2021 Tao Tbr7 - "Lucille" Mods so far- Brozz swingarm, 21" front rim (Bridgestone Tw302 rear/Dunlop D606 front tires), Digital gauge cluster, pz30b pumper carb, after market hand guards, aftermarket brake and clutch levers, round fold away mirrors, Fly handlebars shortened slightly, 13t front sprocket 2009 Q-link Legacy 250 1982 Suzuki GS1100ES - "Jolene" |
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03-09-2021, 05:51 PM | #7 |
Join Date: Feb 2021
Posts: 994
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I didn't run the break in oil out on the road, but I did start it up on it several times, and then changed to the 15w40 Rotella. I noticed that the factory oil didn't come up very far in the sight glass while I would hold the bike straight up. I accidentally put a little too much oil in mine when I changed it. It comes up a hair more than halfway on the glass. I didn't take any back out because just barely leaning the bike puts the oil level down to about halfway on the glass. I was pouring from a gallon jug when I did mine. Are you a little over full ? I figure that if one was very much too high the windage may be costing you a little pep.
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03-09-2021, 06:34 PM | #8 |
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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The oil is unlikely to cause a sputter during wot. If it were mechanically related, it should present itself outside of a specific scenario like that.
As was mentioned, the valve lash should be .05mm or .002inch. If you set the lash to .005inch, that is rather big on the gap, and could explain a little bit. I would start by double checking the lash.
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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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03-09-2021, 06:46 PM | #9 |
Join Date: Nov 2020
Posts: 21
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I set it to the factory size in the manual, if I added a zero here thats my faulty memory.
I haven't had a chance to check the valves yet, stupid real life getting in the way of my bike .... Any ideas how much longer I'll have to keep checking valves? Or is that just gunna be a weekly maintenance item? |
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03-09-2021, 07:53 PM | #11 | |
Join Date: Jan 2020
Posts: 287
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Quote:
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2019 Z 400 2020 Tan Recon 2021 KLX 300 2022 GPX FSE 450R |
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03-09-2021, 11:16 PM | #12 |
Join Date: Aug 2019
Location: Central Ohio
Posts: 297
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Not to doubt anyone, but.make sure you are setting your lash on a COLD engine on the COMPRESSION stroke at TDC.
I made the mistake once and the bike ran like shit for a.couple days until I figured out what I did. I thought it was carb related at first. |
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03-09-2021, 11:24 PM | #13 |
Join Date: Aug 2019
Location: Central Ohio
Posts: 297
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Also, your manual will state .05mm for your clearance. That is great if.you set both intake and exhaust to that spec.
Some guys will change it a little, MegaDan could speak more on the reasoning behind that, for example, .07mm-.08mm for exhaust, .05-.06mm for intake. Seems intake runs tighter than exhaust for a reason I haven't grasped yet. Either way, if you set it as manual says at .05 intake and exhaust, it will be fine. |
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03-10-2021, 02:20 AM | #14 | ||
Join Date: Apr 2017
Location: Omaha, NE
Posts: 8,100
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Quote:
I mainly just suggested to double check the lash or the reason that gwowzer stated. It's a common mistake that has been made, so I just wanted to cover that base. For all I know it could be ok, but it never hurts to make sure. As far as the bike running differently as it breaks in, China Rider 27 covered that one rather well. Not only does the better ring seal help draw in the intake charge, it also gets more efficient at expelling the exhaust. The valve seats and valve faces at this point are also sealing just a teeny bit better as well. This can sometimes cause a bike that ran "ok" with almost no miles start to show changes in jetting needs. This effect is also exaggerated a bit if the valve lash was not set from mile 0 and the valves were not sealing before. As far as a previous question of yours. the 15w40 oil is likely not any thicker than what came in it, which if I understand is 10w40. Both oils have the same hot viscosity, so there isn't any real difference there. My main goal is to simply try and separate issues so they can be approached individually, if for no other reason than to eliminate one thing to move on to the next. Attacking multiple things at the same time can cause more problems than it solves. So I am starting with the easiest and most likely things first. Valve lash takes a few minutes to double check, and can't hurt anything. Quote:
I set my lash at .05mm intake and .07mm exhaust, but my engine also has way higher than stock compression, port work, a cam, an ignition advance key and an adjustable CDI, so not only do I have a bigger bang from the cam and head porting, but I also have a much higher cylinder pressure from a later ignition event that sends more heat through the exhaust. On a normal CG engine, setting both valves to .05mm works just fine for most people. They can get away with this because the CG runs fairly mild compression, extremely conservative ignition timing, and your basic cam profile for good smooth torquey operation. They don't make a whole lot of heat.
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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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03-10-2021, 02:26 AM | #15 | |
Join Date: Feb 2021
Location: Northeast
Posts: 934
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From my own n00b experience, I’d say keep an eye on the basics too.
After only 30 miles my chain already needed adjusting. My spokes could use a little fine tuning but I suspect will go out in another couple hundred miles. Quote:
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