How to adjust the jets on motorcycle carburetors

[KEEPNITPG]

I have a cb650sc im making into a cafe have all upgrades and mod'd myself it looks sick and thanks to you i understand more than i did the crude animations helped soo much'

[mrmaxstorey]

@KEEPNITPG Cool glad to help

[KEEPNITPG]

THANK YOU SOOOOOOO MUCH



[altlandf]

By the way my bike is stock. It has the OE air cleaner and exhaust. Most times I used 93 or 92 octane but the problem is back again.

[mrmaxstorey]

@altlandf The majority of problems starting which present as the weather turns cold come from vacuum leaks and weak batteries. I would like to encourage you to watch my video on how to check for vacuum leaks, how to diagnose battery problems, and finally how to select the best fuel octane for your bike. Let me know if I can be of further help or if those videos are unable to direct you towards a solution.

[altlandf]

I live near Harrisburg, Pa. I am having a problem with my Honda CM250C starting when it's cold out. I don't think my bike likes the cold. Most times after the bike warms up it runs pretty good. But today wasn't one of them.  It was about 35 degrees out and the bike idles good but when I put it into gear and try to take off it won't go and starts to pop and carry on. To make matters worse we have ethanol in the fuel. If there's too much in the fuel the engine will run lean. What do I do?

[krayziesensei]

Wow! Very well done and easy to understand.

[nikola25spasic]

Max, looking at the jet sizes for the main on my BS34ss carb the stock is a 130 and it goes up to 132.5, 135, 137.5, 140, etc. Are those jets ending in .5 half size increments? I figure they are but want to get that 2.5 base after adding the pod and work from there.

[mrmaxstorey]

@nikola25spasic You got it, they are very precise. I would suggest getting a set of 132.5 and going from there, you may need to tinker with needle height or even go to 135, its not an exact science.

[Saiph2266]

What would be the symptom if the jets were to big? Too rich right?

And if it was too rich would it be possible to lean it out with lengthening the needle?

[mrmaxstorey]

@Saiph2266 Yes if the jets are too large then the bike will run rich. It is somewhat effective to drop the needle down a bit to lean out the mixture a bit, if that is an option on your bike, however like the video illustrates, adjusting the needle only has an effect on a certain range in the throttle. It will be difficult to get your bike to run well throughout the range just by adjusting the needle. Slow jet, main, needle, intake, exhaust, all need to work in harmony

[ilikesuzuki]

@mrmaxstorey is bogging and hiccup a sign of lean or rich.

[mrmaxstorey]

@ilikesuzuki Sounds rich, altho it could b either. Pull the plugs and look at em, should tell for sure if you are running rich or lean.

[eananstrain]

excellent video, very clear thanks. im a complete rookie on this whole area, but videos like this definitely help me get a clearer picture of where I should be looking to start sorting the carbs out on my own bike (cold / idle / low rpm - tbh i could b looking at a few other factors as well as the carbs!)

Thanks, great video

[mrmaxstorey]

@eananstrain Right on good luck with your project let me know if you need any help with it

[DanBennetto]

Great video! I'm just going to knock out all my baffles so here we go!

[mrmaxstorey]

@DanBennetto Good luck Dan!

[Michiganborn1969]

I went ahead & put RTV on both sides of the gaskets & the bolt areas. Seems to be running like a champ now. I have a few more test to do when I get the chance. At the moment my New bike is taking up a lot of my time & also I get busy @ work on the weekends. Btw the New bike is a 2011 V Star 950 tourer

[Michiganborn1969]

@Michiganborn1969

oh btw, after I got everything back together on it, I looked a little closer at the directions on te back of the RTV. It said "NOT recomended for parts in contact with fuel" Since the carb boots have an air/fuel spray mixure going though them do you think it will be ok? I used the Red Permatex RTV gasket maker.

[mrmaxstorey]

@Michiganborn1969 Yeah, that and the heat is what eventually breaks it down. But it takes about a year in my experience

[Michiganborn1969]

@mrmaxstorey

Yeah & it gets REAL hot here in the valley with little humidity. So She was a great trainer bike for me but can't afford parts or the time into it anymore since my job has me more busier then a 1 legged man in an ass kicking contest. Thanks as always for all the help.

[Michiganborn1969]

Btw, what's the best, easiest way to clean up an old bike & to get into all the little nooks & cranes on things like the cooling flares to remove old sludge, oil & other gunk? I have a steam machine & some gunk degreeser. Would a small wire brush also help?

[mrmaxstorey]

@Michiganborn1969 Ive never done it, but a sand blaster loaded with baking soda is supposed to work amazingly well. Water washes it away really easily, no sand all over the place. My air compressor isnt strong enough to power one or thats what I would be using all the time.

[Michiganborn1969]

I guess after today I won't be having these issues with carburetors anymore. Just got my Maxim out of the shop after being there a whole month & they told me there's nothing more they can do to find the replacement carb boot joint. The ones I got off Ebay were worse then the ones I had. So I'm done spending $ on it and going to go pick up my NEW bike later today. A '11 Yamaha V Star 950 Tourer. Carb problems solved lol.

[mrmaxstorey]

@Michiganborn1969 You can always slobber a little gasket maker into those boot cracks and then rev the engine, the vacuum should pull the material into the cracks and allow it to harden in there. Thats my last resort technique.

[Michiganborn1969]

@mrmaxstorey

Update: I went & RTV'ed the hell out of the carb boots (isolators) on the end that connects to the intake manifold & looks like the base of a thermostat housing on a car, put evrything back together, fired it up and now my Maxim is running great. It urks me that a pro shop couldn't do in a month that I got done in like a day worth of time & a $4 tube of RTV. I just need to do a few more test to make sure I'm finally firing on all 4 cylinders when I get a chance.

[mrmaxstorey]

@Michiganborn1969 Glad to hear it. Remember this is not a permanent permanent fix, you may have to re-up it from time to time as it flakes off, before you can find a decent replacement set of boots.

[Michiganborn1969]

@mrmaxstorey I'm just hoping to get her running good enough to when I sell it I can get a good price for it. Good replacement boots are next to impossible to find & that's why the shop didn't want to work on it. The boots I got off Ebay were in far worse condition then the originals. I'm just going to take the cash from the Maxim sell off & put towards accessories on my new Star 950

[mrmaxstorey]

@Michiganborn1969 Sounds good to me!

[excriminal1]

very informative and really well explained, i think i will keep coming back to you for information as you explain it really well. thanks for the info :)

[mrmaxstorey]

@excriminal1 Glad to help!

[Brahbarian]

Any chance you can do a how to valve adjustment on that gsxr? What year is it?

[mrmaxstorey]

@Brahbarian Haha what year is it. Thats a good one. Its a 1990 block with 1991 heads and carbs (I think) on a 1989 Katana frame with a 1988 katana tank. So... I have no idea. Jetting it properly has been pretty tough. And yeah I do have a valve video in planning, but first I need to get a bike that needs a valve job done, but trust me next time I do a valve job I will post it.

[kelly68934]

I really enjoy your videos, Max. Great job! You mentioned a website for carb parts, but I didn't write it down. Care to share your parts source since I can't seem to find it watching the video again?

[mrmaxstorey]

@kelly68934 Sure no problem I buy pretty much all of my jets at jetsrus(dot)com

[jimmyfingers95]

Your videos are super informative. Keep up the great work! ...much respect..

[mrmaxstorey]

@jimmyfingers95 Thanks dude glad to help

[zx4133]

Dude thanks so much for all your videos! Quick question - I have an 82 Honda CM450C that has 2 main jets, a primary (stock is 72) and a secondary (stock is 115, this is the jet that the needle goes into), and then a slow jet (which I think is just another name for pilot jet). I have pod filters and straight pipe exhaust, so should I increase both mains by 5 or if not, which do I increase? Any help is MUCH appreciated!

[mrmaxstorey]

@zx4133 Well, since you have 2 main jets I would increase them both by 2.5 and see what happens. You may need to go up a step again, shim the slides, and/or increase pilot jet size. But start the mains at 2.5 more if you can.

[Michiganborn1969]

Lmao. mikunis sounds like a medical term for something in the sinuses lol. After watching this video I suppose this biggest pain in the ass to a newbie would be to get ALMOST everything tuned in correctly and have to disassemble everthing, dial in the correct setting/s again & reassemble everything.... Again.

[mrmaxstorey]

@Michiganborn1969 Haha its not just a PITA for newbies, its still a pain for me. Thats the way its done tho, my gsxr has had its carbs off at least 10 times while I chase around the dead spot...

[Michiganborn1969]

@mrmaxstorey Holy cow! 10 times?!? Anymore & I think you might be able to do it blind folded lol.

Btw, how did you get so bike smart anyway? Years of trial & error or did you go to

School for all your know how?

[mrmaxstorey]

@Michiganborn1969 Yeah, 10 times and probably more to go, Im chasing around this dead spot it is a major pain. And no I never went to school for this, just hung around bike junkyards, bought a bunch of manuals and books, and talked to old bikers about that they do. That accounts for all my bad habits lol

[Michiganborn1969]

Great lesons Max. Always good to learn something new even though you kinda lost me at 13:18 when you mentioned about reading a number on the pilot screw b/c I have no idea what those numbers (1.37?) mean or represent.

[mrmaxstorey]

@Michiganborn1969 The numbers represent the size of the aperture of the jet, altho 1.37 is not a common size for mikunis. You should be reading something in the 30-50 range.

[spelunkerd]

That's a brilliant summary. I'll have to review this a couple of times to get the most of all you said.

[mrmaxstorey]

@spelunkerd Thanks friend, glad to help

[FearMeSuckers]

This is a very usefull video, i've been having some trouble with my bike, have clean the carbs and it helped a lil bit, but still not decent enough, after ur explanation in how the needles work, i think finally i know where the problem is.

Damm thing was poping alot when i let go of the throtle, and gets a little slugish on the 1/4 band but then recovers and goes normally, guess its time to take them apart again. suzuki bandit 600cc '01 btw

[mrmaxstorey]

@FearMeSuckers Glad to help I hope you figure it out

[sverkere]

Thx Max for demystifying this part of taking care of an old non-original bike. Best carb video on the tube! On my GSX 1100 -83 it sits a 4-1 exhaust and open air box (cover removed). This is standard for these types of motors. Your video instructions is great in all respects except recommended main jet size. Going up just 2 steps is too small for some bikes. My original is 107.5 and a good main jet size is somewhere around 122.5 - 130. Anyway thx again!

[mrmaxstorey]

@sverkere Haha yeah thats why there really is no hard and fast rule for jetting, because so many different bikes vary in their preferences. It is important tho to take tiny steps when you are jetting for the first time, if you just leap around by 10 jet sizes then you'll never get it right. I have tons of jets lying aorund which is good, because they definitely take some tnkering

[sverkere]

@mrmaxstorey By the way Max, where is the donate button ?

I would not be surprised some of the good guys here

clicking that once or twice! :-)

[mrmaxstorey]

@sverkere Haha I appreciate the sentiment, but those ads on the side of the screen are the donate button... you guys keep me in beer

[boondockdread]

awesome. im so glad youre doing these videos for us

[mrmaxstorey]

@boondockdread No prob dude

[Nerdsugi]

You da best bro! ^_^

[formegolf]

Great Video as always Max. Keep up the good work. You should be any instructor getting paid for it. I know you like helping people but you have a gift that many don't have and I'm sure your fans feel the same way.. :0)

[mrmaxstorey]

@formegolf Haha its all about paying it forward man. Youtube teaches me far more than I teach it anyways... its good to keep the info and good energy flowing around. Glad to be of any service.

[sobeyar]

Great video. I think I finally understand carbs now. Way to keep it interesting.

[mrmaxstorey]

@sobeyar Glad you found it useful dude

[Inthisma]

First comment  woo hoo