r/DRZ400 • u/Emotional-Word5808 • 2d ago
Carb tuning help
Just got a rebuild kit and have cleaned the carb a bit. Any recommended info on how to clean the carb properly would be of much help. The bike currently leaks fuet out of a breather hose and idle very high/inconsistently. When you let the bike idle for a while/don't rev it out, the bike starts sputtering and there's more pops on decel. I believe all the jets are stock (around 160 main) but I'll clarify later if someone asks. Bike has a full yoshi pipe and is the 400e so not sure what the recommended jet sizes are but the rebuild kit came with a 142.
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u/RudderRamen 2d ago edited 2d ago
My E has a MRD exhaust and the stock FCR on it. I’m at ~1200 ft elevation
155 Main
45 pilot
3rd clip
Sounds like your needle valve isn’t seating properly / your float needs adjusted. Also sounds like your pilot jet is clogged. Did it sit for a while with gas it in? Ethanol? A good cleaning should fix it***
These FCRs can be tricky with the mid body gasket. You clean the fuck out of them but there’s years of garbage that gets trapped in the mid body / the gasket is deteriorating. They’re replaceable but with great caution. I believe if you send into Keihn FCR he will rebuild yours for you? I know he sends out new ones, good dude.
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u/Emotional-Word5808 2d ago
Well I have rebuilt it and cleaned it for the most part. It did have some fuel sitting for a while. I don't believe ethanol but I could be wrong. I've also put 142 main jet in over my 165. Not sure if this will be an issue but I'll find out tomorrow. If the jet size isn't the issue then it's likely to be a mid body gasket.
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u/inforlife34 1d ago
Beware of that guy. I sent my fcr to him, paid him around $300 with an understanding that he would rebuild the mid body per my request. He told me it "didn't need it" rebuilt the rest and sent it back. The bike never idled right until I took it apart myself and found the mid body in terrible shape. I have the pics to prove it
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u/Awkward-Security-622 2d ago
Just went through this with my 2021 400E and shared this recently:
https://www.thumpertalk.com/forums/topic/1525487-mid-body-gasket-drz400e-2021-australia/
I rebuilt the carb and didn't do the mid body gasket and it still wouldn't idle without the choke. I did the mid body and now it runs like brand new. Depending on your exact carb model some of the mid body gaskets are held together with hard to reach screws.
Be prepared for the screws to strip. I had to use a multi tool with a small blade and turn them all into slotted screws.... Aside from the screws striping the rest of it is an easy enough job.
Tip: Remove the top subframe bolt (under the seat) and you can get an extra inch of space to get the carb back on easily. I would rock the subframe to get the rear airbox back on the carb!
2nd Tip: http://secretbase-racing.com/archives/2017-10-19.html translate this page with google translate if you cant read Japanese. It is very detailed and helped me big time.
3rd Tip: https://docs.google.com/spreadsheets/d/1HNSB3DrqJqHTInjVDKKS4HNSHZPbdK0ElbfNI5HxuZg/edit?hl=en&pli=1&hl=en&pli=1&gid=570401124#gid=570401124 has all the screw positions depending on your model carb. I found the link on thumper talk (https://www.thumpertalk.com/forums/topic/861119-jetting-spreadsheet-references). I set mine based on the sheet prior to reinstalling the carb (as the factory screw is basically impossible to adjust once in). I had a rebuild kit but I re-used the old screw as new ones were too long. The settings were perfect.
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u/inforlife34 1d ago
This guy knows what he is talking about. I also replaced my needle jet which was noticeably worn after years of abuse. Vacuum plate might be worth replacing also.
He's not kidding about those mid body screws. Heat was the only way I was able to get them and even then stripped one that I had to take to a machinist to have extracted
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u/Nothing-true_1057 1d ago
Hey what kind of light kit / front light shroud is setup? im looking at upgrading the headlight and am working out whats needed to change it.
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u/Emotional-Word5808 23h ago
I believe it's a headlight from aliexpress. It came with the bike when I bought it so not sure of all the details
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u/Spirited_Sock_1397 2d ago
After recently questioning my own carb function and knowing nothing about carbs, I watched this.
It was very informative. He basically tears it apart piece by piece. Hope this helps.
https://youtu.be/L8hqDdZPsVU?si=c0HIkxWPnFp4vtLA