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Discussion Starter · #1 ·
Took my newly acquired 04 450r out for the first time today. It has full HRC kit, full sparks exhaust. The HRC lid is on and it's running the stock filter which was clean. O.K., it feels great off the bottom if I snap the throttle to full open, no miss and it starts pulling strong. The problem is about the time I'm guessing I should feel the HRC cam really start pulling, it starts bogging on me. Also letting off at high RPM produces no crackle or backfire of any kind. I don't know what jets are in there now, haven't looked yet, but I'm pretty sure it's the standard HRC kit setup. I have a feeling what the problem is, but wanted to get some feedback of what others think...
 

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What size main jet do you have in it right now, also what is you altitude?
 

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Lord of Combustion
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too small main jet? rev limiter? too much oil on air filter causing over mimicking choke at high revs? ..........mixxer
 

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Discussion Starter · #4 ·
Definitely not the rev limiter, I've bounced my EX off it enough to know that feeling LOL. Luke - I'm about the same as you I would think, I'm about 10 miles outside of Louisville. I assume the main is a 185, but not sure. My guess is that I'm a little lean on the main because I think if it was rich it would bog down low when I opened it up initially, but it's not until the air flow is maxing out in the upper rpm's that it bogs. The problem with that is when I let off at high rpm there's no crackle which there usually is when your lean, so really I don't know - I just know it's sucks because just as I feel the cam start to give that extra pull, it bogs...
 

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Lord of Combustion
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the main jet only works at high rpm\max airflow conditions. when you crack the throttle open on a pumper carb you momentarily go super rich since the pump shot is what is dominating your jetting.

on jetting mine (on a dyno WITH an afr meter) a 185 is so rich it won't pull max rpm. max hp & torque on mine are with a 165 main

how about throwing us a bone and actually pulling the main and telling us the number? swag method only goes so far.

.................mixxer
 

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Discussion Starter · #6 ·
Can you get to the main without taking the carb off like you can on a EX? I haven't even looked yet and can't right now(at work). Hopefully so...

mixxer - you have me thinking I might be too rich now.

I thought the jet (or combination of jet and needle) that fuel is being pulled through was completely dependant on throttle position, not rpm's. So if I'm at 2500 and snap it open then boom I'm on on the main jet only. Although it would make sense that it needs to pull more fuel through at WOT 6000 rpm vs WOT 2500 rpm...
 

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there are 2 philips head screws that connect the carb to the air box and motor, so loosen them and you can twist your carb towards you ( shifter side ) and pull off the large 17mm bolt on the bottom. the main jet is in there, its a 6mm 6 point. pull it out and look on the side, it will say what size it is, it should be a 185 if its the hrc jet.
 

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Originally posted by mixxer@Sep 13 2004, 11:26 AM
the main jet only works at high rpm\max airflow conditions.  when you crack the throttle open on a pumper carb you momentarily go super rich since the pump shot is what is dominating your jetting.

  on jetting mine (on a dyno WITH an afr meter) a 185 is so rich it won't pull max rpm.  max hp & torque on mine are with a 165 main

  how about throwing us a bone and actually pulling the main and telling us the number? swag method only goes so far.

.................mixxer
Mixxer...
You also have me thinking here as well, just as you do in all of your post's.


But I am currently running an HRC kit minus the cam, a full system, and the stock airfilter. My jetting is HRC needle on 3rd clip position, 185 main jet, stock pilot and 3 turns out on the air screw. I have thought I was rich several times, just because a 185 is pretty dramatic compared to stock, but if I go any leaner on the needle, or with the main jet, it still runs alright, but it gets very warm which scares me out here in the 100+ day's we have.

Can you elaborate a little more on your altitude, and what circumstances are you running the 165?

As desert_450r said... I would not run a 165 out here, but it does throw some "aces" on the table... ^_^
Thanks
Dave
 

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Its been awhile since i've had the stock carb but I think I was running either a 188 or 190 main jet with the lid off, and I believe 2 1/2 turns out from closed on the air/fuel screw and it was running great. you may have a piece of dirt in your main jet, take it off and make sure it is clean.
 

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Lord of Combustion
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a very high comp piston has the effect of richening up your carbs fuel delivery without changing any jets. usually jetting that was slightly lean becomes correct when you bump compression. the 450r isn't quite the same since the stock air box snorkle is actually smaller than the carb bore, hence the giant jet upsize needed on lid removal.

a long duration cam usually has the opposite effect, unless you also increase compression, the jetting will need to be richened.

i use a 13.8:1 piston, live in michigan, and have a slightly more radical cam than the hrc .

usually for best power and with a safety margin air\fuel ratios of 12.5 to 13.7:1 are best (stochiometric is about 14.7:1). best power with mine comes in between 13.75 and 14.5:1 using the 165 main , admittedly pretty lean but if i use a 180 it loses about 3hp from 6000 to redline (i actually prefer torque curves but the world usually speaks hp). since sometimes i would sell left nu## for 3hp across a band like that i'm leaving the 165 in and keeping my fingers crossed.


unless your setups are exactly the same this info isn't totally useful (i know none of you are running the exhaust i have on mine, yet) but that's the lowdown on mine wth the stock carb. hope some of it is useful.
..........mixxer
 

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Lord of Combustion
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i forgot to mention that if your machine pops or backfires on deceleration\ chopped throttle conditions , you are usually too lean on idle fuel screw or pilot jet

......mixxer
 

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Discussion Starter · #12 ·
O.K. - I *finally* worked on my jetting today and am still having a stutter on the top. The main was a 190 when I pulled it and I have worked my way all the way down to 172 and it feels like it's getting closer, but it still stutters and I'm starting to get concerned about going so low. Has anyone heard of this low of a main with HRC kit, including lid and a Sparks full pipe? Will adjusting the air screw help me out any here? It's currently 3 turns out. Anybody thing the problem could be the needle position? I haven't checked it out yet - but it should be the HRC needle on whatever the normal position is - I think 3...
 

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Lord of Combustion
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never trust a dealerships settings. check it out for yourself..i didn't use the hrc needle since the high compression made enough signal strength to make the stocker effective. i would feel safe with a main as low as 170 with your setup since you have felt improvement at each step..............mixxer
 

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Discussion Starter · #14 ·
Thanks mixxer - do you think adjusting my air screw should have any impact on way or another considering it's only at max throttle??
 

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Lord of Combustion
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not so much. 2.5 turns seems to work for me.
 
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