HMF + Stock Main + 40 Pilot = scary... Please read...

[maxfior]

So, I got a good deal on a HMF slip on from a guy on this forum. Tossed it on this afternoon, temp was maybe 40*. Started okay, let it idle for about 5 minutes then took it for a spin. Seemed okay, but not perfect (as I would expect with the cold weather and stock main, stock-ish tunning) so I took it back to my shop... After dinner and some barn work, I started it up again, rain pretty bad, idle was wack and it would not rev up. So, did a little searching and found that others too had this issue.
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FYI, running my stock pipe with a #40 pilot and stock main (148 I believe) seemed pretty good, although starting was still not perfect, it was okay when things got warmed up...
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#40 pilot and stock main with HMF slip on seems to not be too well. (colder air temp maybe too?) My air box is also open. I'm going to follow HMF and others suggestions with a #42 pilot and a #152 main. I guess what I'm wondering is, are others in colder parts of the states with sort of the same setup (pipe, air box mod) having okay luck with that combination? I am also considering running the quiet core when trail ridding. Did any of you have to re-jet (down-size) when installing the q-core? Or can I just leave in #42 pilot and #152 main all year. I plan on ridding in temps 40-90 (or so...)... The lovely world of jetting...

[f150mann]

hmf pipe and no lide? dude get like a 158-160

[maxfior]

Originally posted by f150mann
hmf pipe and no lide? dude get like a 158-160

Well, I have a lid, but there is a custom pre-filter on that I made... But it still flows lots of air... Do you really think that I should put that big of a main in? I do have a 158, 160, and a few others... I just want to try and get it right the first time. You guys still think that a 152 is too small? No other mods then the pre-filter and pipe. I'll have to double check again, but HMF says to run 42 and 152 and I'm pretty sure that's with out the lid too, what do you all think, Thanks.

Max

[Wheelie]

IMO--use a #40 pilot and a 155-158 main.

[limetimeracerII]

You definatly need a bigger jet. I would start out with a 152 and go from there.

[hornetgod13]

With that custom lid and a HMF slip on, it should be atleast a 155K and perhaps a 158K as cold as it it there.

[badcarz]

I ride mostly the dunes here in oregon so the temps are usually 40's in the winter to 70's in the summer. Stock 400 with WB e2, k&n and no lid. I'm running a 42 pilot and a 158 main. Plug looks great, no starting problems and runs strong.

[maxfior]

Originally posted by badcarz
I ride mostly the dunes here in oregon so the temps are usually 40's in the winter to 70's in the summer. Stock 400 with WB e2, k&n and no lid. I'm running a 42 pilot and a 158 main. Plug looks great, no starting problems and runs strong.

Again, THANK YOU all for all the help! This is a great place! I figure I'll do the #42. I should have just put that in the carb right from the get go, since the #40 does okay, but still not that great for cold starts, heck, my 200s 3wheeler is jetted so rich that one pull choked and that thing fires right away, turn off choke and it'll idle all day in 20* weather. ...and, after reading what badcarz is running, pretty much the same as me, I might try a 158. I've got one around here somewhere... I'll let you know what happens, I'll have to find some time do install the jets and it's mighty cold in my shop... I better think about a heating solution next winter... brrrr.... Again, thanks everyone!

Max

[espergre]

hey, im in southeast mi, i have a hmf sport series, modded air box lid. if you put in a 158 you most likely will be ok now with the cold weather, but come summer, you are gonna be too rich. id go with a 155. good luck man

[maxfior]

Originally posted by espergre
hey, im in southeast mi, i have a hmf sport series, modded air box lid. if you put in a 158 you most likely will be ok now with the cold weather, but come summer, you are gonna be too rich. id go with a 155. good luck man

Thanks man, I'll give that a try. I talked to Jim, or Willy, or someone over at HMF and they said to give a 155 a try too. I did notice that one of my pilot jets (#42) seems to have a little burr or imperfection on the inside, I don't know if it'll make much difference, I should email jetsrus.com since that is where I got my jets, I have a feeling that they are selling China made jets... What do you all think? thanks again!

Max

[espergre]

i would def get that jet replaced, the difference between a 38, 40 and 42 is very small. even a grain of sand in your jet can effect your fuel flow. have them send you a new jet. jetsrus only uses keihn jets to my knowledge, they are the only place i rely on for jets.

[badcarz]

We get spoiled here on the coast when it comes to jetting. The air is pretty consistant for stock bikes. Lots of oxygen in the air year round. I agree that back in the midwest during the dog days of summer a 155 might be the ticket.

[flatl1n3r]

I have an HMF Slip on and UNI filter with open box and my setup is 155 and 40. Runs great so far through the cold months, we stay around 30-40 degrees here. The spark plug stays light tan so it might still be a tad lean.

[Pipeless416]

when i had a stock carb and an hmf, open lid, 10.8:1 piston, and a k&n filter i ran a 160k main, 42 pilot, stock needle setting, and 2.5 turns out of the a/f screw. it ran like a champ in all weather, with or without the quiet core. im 720 feet above sea level, and temps range from 10-95F.

[maxfior]

Originally posted by Pipeless416
when i had a stock carb and an hmf, open lid, 10.8:1 piston, and a k&n filter i ran a 160k main, 42 pilot, stock needle setting, and 2.5 turns out of the a/f screw. it ran like a champ in all weather, with or without the quiet core. im 720 feet above sea level, and temps range from 10-95F.

Good to know, thanks a lot guys. I'm going to go with a #42 pilot and a #155 main. I really don't want to take a part the carb in the summer to switch jets unless I really have to. Plus, I have not been doing that much cold weather riding, that's what the junky 3wheelers are for... I think this is going to be a good thread for all people trying to baseline their jetting with mild mods, pipe, filter, box, etc. Thanks again!

Max

[Pipeless416]

Originally posted by maxfior
Good to know, thanks a lot guys. I'm going to go with a #42 pilot and a #155 main. I really don't want to take a part the carb in the summer to switch jets unless I really have to. Plus, I have not been doing that much cold weather riding, that's what the junky 3wheelers are for... I think this is going to be a good thread for all people trying to baseline their jetting with mild mods, pipe, filter, box, etc. Thanks again!

Max

to change the main, you can simply loosen the clamps on both sides of the carb, turn it towards you, and remove the 17mm cap on the bottom. much easier than taking the entire float bowl off :)

[maxfior]

Originally posted by Pipeless416
to change the main, you can simply loosen the clamps on both sides of the carb, turn it towards you, and remove the 17mm cap on the bottom. much easier than taking the entire float bowl off :)

Oh man! I'm going to try this FOR SURE! Even though I really don't mind too much taking things apart, this will be a hand little trick, is there anything else I have to watch out for? Thanks!

Max

[espergre]

this is a great trick, be careful when putting the new jets in, it is possible to over tighten them and break the threads off the jet. very hard to get out then!

[maxfior]

...Well, I put in my #42 and #155 and the EX is still running poorly. I think I might have to get a new plug, since everything else seems okay. I even went back to the #40 pilot and the engine is still surging and popping. It will not idle at all, talk about frustrating!! :rolleyes: The things we do for performance gains... The temp is still pretty cold in my shop, I do have a fuel heater going and it is keeping the air temp up some-what...
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What do you guys think, just hold off until I get a new plug before messing with the carb more. From the looks of it, this plug looks to be the same age as the quad. 3 or so years old. I did check the gap, and it was a little off... and when I did a plug test, holding it to the side of the engine and cranking the spark was pretty good, at least I thought so... blue in color. It jumped the gap okay, but I know how a spark plug will perform differently under compression, so that is why I want to try a new one... Any thoughts guys? When I had the carb apart again it looked nice and clean, no dirt or anything. Hoses were in good shape and routed properly... Air filter is pretty clean, I changed it not too long ago... So, any other thoughts would be great, before I pack it in for the evening and just get a few new plugs in tomorrow. Thanks again for all the help guys! :)

Max

[maxfior]

...Well, I kind of feel like a jack ***... I pulled the plug again and notice that the top part of the plug rocks side to side. I must have cracked it loose the other day when checking the color. This was after my first ride. After that is when I was having all the issues. So, since the plug is aced, compression is going right past it... So it looks like a new plug will slove all my issues. I'll keep you guys posted... :)

Max

[Pipeless416]

Originally posted by maxfior
...Well, I kind of feel like a jack ***... I pulled the plug again and notice that the top part of the plug rocks side to side. I must have cracked it loose the other day when checking the color. This was after my first ride. After that is when I was having all the issues. So, since the plug is aced, compression is going right past it... So it looks like a new plug will slove all my issues. I'll keep you guys posted... :)

Max

haha good catch. and when you take the cap off the carb, just remember to turn the gas off and either turn the little drain screw so the gas will empty out of your float, or run the carb out. same thing as if you were taking it apart, but its much easier to forget.. its not cool to leak gas with my black engine :o

[maxfior]

Originally posted by Pipeless416
haha good catch. and when you take the cap off the carb, just remember to turn the gas off and either turn the little drain screw so the gas will empty out of your float, or run the carb out. same thing as if you were taking it apart, but its much easier to forget.. its not cool to leak gas with my black engine :o

HA! Yeah, I pretty much forget to drain the carb (well, all carbs that I work on) when I'm working on it, but I do keep an thick old rag under it to catch all the fuel. Your right though, it's not fun to forget silly things like that... :)

Max

[maxfior]

Problem solved. IT WAS the plug and I went with a #42 pilot and #155 main with the HMF no quiet core (yet) run AWESOME! Thanks for all the help guys. I look forward to roosting when we get some more snow! :D

Max

[blinkjs]

Max,
Glad you got the jetting figured out and like the pipe.