Honda ATV Forum banner
1 - 18 of 18 Posts

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #1 ·
Some of you may know I ordered some jets to try and eliminate that lack of top end power/throttle response. They arrived but they look rough! Threads are sharp to the touch etc, there just cheaply made somim assuming there Chinese.

Can any of you guys point me in the direction of a decent quality jet suppliers over the pond there? OEM are over £25 each in the UK! OUCH!!

Also, which jets would you advise trying? Sizes, which one to change, change two? Change one? Etc
I’ve never jetted a carb before although my understanding of how they work is now much, much better than a few months back lol.
 

· Premium Member
Joined
·
12,712 Posts
I don't know of any jet kits , Wheeler is the jet guy ----did you ever check the slide /plunger diaphragm , I just went thru no top end and Manny put me right on it ------- don't you have a snorkel ? did you try to run it with the air box lid off ?
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #3 ·
Yeah I tried all that, airbox kid off and it gets worse on top end. I’m assuming it’s to much air flow and under fueling. The plug indicates that it’s running slightly lean too.
I was thinking just go up a size with the main jet?
It’s very close but needs that little bit more.

Edit, yes, all this started after snorkelling
 

· Premium Member
Joined
·
12,712 Posts
what size pipe are you running , all my 300 have 1 1/2 " the whole way except for a 1 1/4 pipe where it goes into the air box --- take a red shop rag and foil it twice , tape it over the hole on the end of the snorkel so it sucks air thru the rag and restricts the air , take a ride and try it , then foil it 4 times , 6 times and see if restricting the air makes it run better
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #5 ·
That’s a good call. When I first fitted the snorkel it was 1 1/2 straight through, ran like carp! You advised to use the 1 1/4 into the airbox, ran a lot better. Moved the clip a notch, then another, ran even better! It’s just that last little bit that needs tweaking.
 

· Premium Member
Joined
·
12,712 Posts
a couple of my buddies have Yamahas 400's , and they seem to be affected bad when you snorkel them , one has a reducing bushing in the end of the pipe to restrict the air -------- I have been lucky with 300's , 4 are snorkeled and didn't give any troubles with carb adjustments afterwards
 

· Premium Member
Joined
·
4,390 Posts
JetsRus. Im bies because they are local to me. (Only about an hour away) but they have a very easy to navigate website and straight forward pricing. Cant say 100% sure they ship international? But thats where i get all my jets from. And i purchase alot lol
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #8 ·
Thanks guys.. I’ll try reducing the size of the inlet slightly as you suggest fish. Failing that I’ll google search ‘jetsRus’ and see what they have to offer.
I can’t do a lot yet as I still have the side casing off doing the GR but it’s definitely the next job on the ‘to do’ list.
 
  • Like
Reactions: XplicitRacing6

· Registered
Joined
·
1,759 Posts
For full performance I'd go back to the larger snorkel pipe and increase the jet size to run better. It sounds like you will need one or two sizes larger than the one you had in it for the 1 1/2 inch snorkel. I am cost plus 20% and tax exempt on all OEM ( for my shop) Tell me which two or three you need. I can mail it to you. You can mail me a check after you receive the jets..... I just called my source before posting to get the price. My cost is $3.05 per main jet. Hope this helps.
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #11 ·
That’s very kind of you, I have no idea what the OEM jets are if I’m honest, it’s been a while since I had the carb out now. I’m sure @retro will know off the top of his head, he’s like a Honda Thesaurus! lol.

Most things I have shipped come in a jiffy envelope, I’ve sent the little ones, 6x5 inch for £3 in the past, that’s around $5 I think isn’t it. Either way, I don’t mind paying a little extra for a quality part over a China cheaply.

I’ll check in my FSM and get back to you.
 
  • Like
Reactions: misterclean59

· Premium Member
Joined
·
5,960 Posts
The stock main jet (except high altitude) is #120 on 88-90 300s, while the stock main jet on all 91-2000 300s is #125. Stock location for the clip on the needle is the 3rd groove from the top on all.

I wish I had some main jets for ya Sam, but I don't. The NOS part we talked about arrived today and its headed your way on Monday... let me know if I can stuff the package with anything else? Or alternatively, (if you wish) I can hold up on the shipment for a while in case something else is wanted/needed before you get the 300 back together..? I'll get you some jets if you wish...?
 

· Premium Member
Joined
·
1,039 Posts
Sam, I have a multitude of Mains.. let me tell you.... I can mail what EVER size you like...

SO what I would like to know... Can you give a detailed description of your issue....

Stock Needle? Drilled out Vacuum Piston?

What size Main now?

Does it have a flat spot top end? Rev out but go no where? Lack of power? Colour of plug? Have you done plug chops???

Also, what's your exact elevation & relative humidity? That plays a big part too!


Don't get me wrong, I"m NO expert but like fish said, I've F&$#ED with my jetting and learned soo much it's stupid! lol....
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #14 ·
So everything in my carb is stock, I’ve changed nothing other than an OEM carb kit several months back.
I have a snorkel, and my issue started since fitting it. A flat spot between 3/4 & WOT.. I lowered the clip twice, so I’m two down from stock and it’s a LOT better, it just needs that little bit more

I haven’t done a plug chop, the colour of plug is on the lean side, you’d ride it a short distance but not for miles if that makes sense. I did check the elevation some time back and its jetted to suit the UK.

I’ll get a picture of the plug later on and check the FSM for stock jet sizes
 

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #16 ·
If lowering the needle helped then you are too rich........a typical symptom of a snorkel
I lowered the clip, so raised the needle.

I checked the plug, a nice tan colour on the electrode but a small amount of carbon (black) around the outer edge of the plug. So the circular outer is black and the electrode is tan.
Strictly speaking it’s not the electrode is it but I mean the bit it arcs to.

Sorry for making a hash of explaining that but I’m trying to be as clear as I can, I didn’t have my phone on me when I took the plug out, hence no photo.
 
  • Like
Reactions: misterclean59

· Premium Member
Joined
·
5,072 Posts
Discussion Starter · #17 ·
Haven’t had chance to get the carb off yet to look at jet sizes guys, I’ll get this GR finished and then take the carb out. I’ve got bits everywhere at the moment, I like to get one job done at a time.

I’ll get back to you.
 

· Registered
Joined
·
1,759 Posts
Reading your plug color may be a little more difficult than it seems. Let me explain. Throttle position is crucial when checking a plug color. I'm sure you know about the different circuits in the carb. Each circuit only performs at it's throttle position. You can have very different plug colors like yours does if you are compensating a lean main by over increasing the needle richness. Also it is just an average reading because your are using many different throttle positions during one ride. Plug readings are best for main jets because you need wide open throttle for a true main jet reading. It requires full throttle and full rpm thru all the gears several times. Kill engine at top speed. Stop repeat for 3 or 4 runs. If the needle is way off it can have a minor effect on the main jet reading. Hope this helps.
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top