Honda ATV Forum banner

What am I missing???

3K views 56 replies 9 participants last post by  wheeler 
#1 ·
So some of you may know that my new build has never achieved the same results as my last quad.. I can't handle it... Making me nuts...

Old 94' Honda 300 had 355BBK with 40B Webcam. Topped out at 60mph.

New build is 95' Honda 300 with same 355BBK & 40B Webcam. Tops out at a weak 50mph to be honest. Very weak....


So I've gone thru what I like to think is everything.. and all seems good. So IF I'm right and all is good, what would cause such a loss in RPM & power top gear??

1st-3rd pulls great! 4th not bad but 5th looses power when any incline ect... Plug looks half decent...

I will take ANY advice or tips, or ANYTHING!!!!! This quad should have more power/speed for what it is if you ask me!!!! It's making me nuts that my old one would out run a 420 or 500 and this one is SLOW compared....


Tomorrow I'm going to check my cam timing. Maybe I'm off a tooth?? Gawd I hope thats the issue...
 
See less See more
#2 ·
I would think you know the feel for what you had and what you got , and you say the engine is weak in comparison to the newer one , and it very well might be a problem with the engine but something that fits a part of your problem is that = quote / " 1-3 is great but 4th and 4th loses power "/quote = my buddy just went thru the same thing with a 300 , it ran great 1-3 and fell on it's face in 4+5 , his problem was the clutch , he put a used one out another engine ----I actually rode with him when the problem was happening a couple of weekends back and again Saturday after he changed the clutch and his problem is solved

What is the compression of that 355 kit to start with ? Have you rechecked it lately
 
#3 ·
Now mine is running half decent I’ve found the same, 4th is ok but 5th is a real sloth! I do have a new change clutch to fit though. I’m assuming your friend changed the centrifugal Fish?
Wheeler, I did notice mine got a little better the Richer the mixture was, obviously there’s a point where you can’t richen any further though. Are you using a 350 carb?
 
#4 ·
I say clutch.

When you're in higher gears do you see the RPM's climb without feeling any change in speed or pull?
 
#5 ·
Reading Wheelers signature, it shows he’s already upgraded the clutch to an EBC. Would be odd for an EBC to be bad I’d have thought, there one of the leading manufacturers.
Stranger things have happened though, could be clutch.
 
  • Like
Reactions: wheeler
#9 · (Edited)
Ok, a little more background....

Old one, I always ran Honda OEM clutch packs. New one I chose EBC.

Old one ran stock CDI. New one I tried an eBay, Now Ricks CDI.

Old one had a White Brothers Exhaust. (no longer exist) New one has FMF for 300ex. (larger diameter I don't know..)

Old elevation was sea level. New elevation 2200 upwards of 4000 depending on where I ride.

Old jetting was a 142main. New jetting is a 122main. (due to elevation)

Old tires were 26" Kenda Executioners. New Tires are 26" Zillas. I went saved around 20lbs of rotating mass.


Old quad fired up fine with electric start in cold. This one will not. Like the battery is almost dead as soon as there is a chill in the air. Put new battery in and no difference. Fires up first kick though.....



I'll be checking the timing & compression of the engine to make sure all is good. I have only re-checked the valves once and they were out. Webcam calls for .004 on both intake and exhaust. I have yet to do that. The quad pulls really good like mentioned 1-3. Its not like a slipping clutch in 5th, rather it won't rev out....This is why I"m baffled. I guess I could install the OEM CDI and see what happens. I as well should go buy a tach like Fish and then I can see where I"m at in the gears which may help diagnose my issue.
 
  • Like
Reactions: Goober
#10 ·
my money say's it's the c.d.i. !. reason : if it kicks on first start, but slow on electric start ?, this tells me that ricks c.d.i. is junk, I don't trust any c.d.i.'s other than oem from Honda.
 
#12 ·
With regards to the Ricks CDi’s, he uses stock Cdi's and modifies them for the extra 1000rpm and slightly hotter spark/timing advance. I don’t doubt his work at all unless of course the cdi was bad before he modded it.
Be nice if you could try your cdi in another 300 Wheeler just to confirm it’s not a bad cdi. I’m going to put money on it being a fuelling issue, my 300 is exactly the same as your description, I know for sure mine is a fuel issue as it only happened after I welded a big split up in the exhaust silencer/muffler.
 
  • Like
Reactions: wheeler
#13 ·
a lot of ricks c.d.i's are a china knock off, would not be surprised if he has a dud ?..lol. and I know for a fact, if they kick start, but won't elec start easy ?, this tells me the c.d.i. is bad, i'll bank on this.
 
#14 ·
You mean a lot of Chinese knock offs are branded ‘ricks’... Ricks are Ricks, especially if bought from Ricks.
 
  • Like
Reactions: retro
#16 ·
Pretty sure you’ll find Ricks (genuine) have Philips and the OEM numbers on them, along with an engraving that corresponds to Ricks programming. That suggests, being Philips, that they are in fact modified OEM CDi’s.

I love a good old debate haha.. Can’t teach you old guys :laugh:
 
  • Like
Reactions: wheeler and retro
#18 ·
Ok, well I made the post for ideas, suggestions, & discussion. I will re-install the OEM CDI & see what the results are.

misterclean59 -

I had difficulties dialing in the main jet. I had talked to a custom speed shop. He explained that he sees this all the time. You install a BBK like I have, & have now created more vacuum by the larger diameter piston & compression. So what happens is due to the vacuum increase it pulls fuel faster thru the jet causing a rich condition. He suggested after looking at my plug to keep going down in jet size until the plug looked good & quad ran better. So I kept going down until the top end stumble went away and power increased. I'm running a DynoJet 116 which is equivalent to a Kehien 122. So I'm only 1 size down from stock. I had to do some googling to make sure what he said checked out, and it does. With that being said, maybe I still can go down 1 more jet size I dunno. I'll take a pic of the plug and post it up. No keep in mind it won't be a plug chop, just a general idea how the engine is working...


I also booked in at a speed shop that has a dyno. They are going to weld on a bung, hook up an AFR and get readings thru the gears. Come hell or high water, I'll figure it out.
 
#19 ·
Be nice to get the next jet down and take it along to the dyno with you, dona run as it is now and then a run with the lower jet.

I’m still learning so this is only what I’ve read... I was always under the assumption that folks used the 300ex carb or 350d carb when running a BBK. Have you considered those options?
 
#25 ·
Yes Its something I've considered. Last build I ran stock carb. But in my quest to get this baby to 60mph & rev out, I may have to try a 300ex carb...
 
#20 ·
 
#21 ·
[/IMG]
 
#22 ·
 
#23 ·
Wants to be richened up a touch IMO.
 
#24 ·
Haha...! You'll never convince shadetree that someone can build better parts than Honda. He'd still deny it even after you tied him to a modded bike and scared all the carp out of his pond! LOL

Honda thinks we all should ride their overpriced and under-performing shopping carts and be grateful! Not me man... stockers are meant for modding every which way but loose! :)

Back on subject... I'll guess that the exhaust is probably a poor match for that motor and its being significantly aggravated by higher elevation and the (over) size of the carb. Getting each half of the combustion chamber (the gas exchange process) working together efficiently may wake that motor up. I'd go back to stock on each side of the valve and alter one component at a time until it can be demonstrated that each of those mods are indeed summing torque production in your target RPM range.
 
#26 ·
Back on subject... I'll guess that the exhaust is probably a poor match for that motor and its being significantly aggravated by higher elevation and the (over) size of the carb. Getting each half of the combustion chamber (the gas exchange process) working together efficiently may wake that motor up. I'd go back to stock on each side of the valve and alter one component at a time until it can be demonstrated that each of those mods are indeed summing torque production in your target RPM range.

This is the one component I was seriously questioning... The 300ex full exhaust. This muffler is straight through where the White Bros had the discs.... It may need more back pressure.. what do you mean stock on each side of the valve??
 
#27 ·
How about trying another clip lower, if it runs like carp low down but pulls hard top end it may benefit that slightly bigger carb.
With the huge split in my muffler I had to bang loads of fuel in, finally got it running great.. welded up the split and it ran like a sack of spuds again! Had to reduce the fuel..

What I’m saying is, with your exhaust, try putting in more and more fuel, see how that goes, if you get it right on top end then change the slow jet to suit or as you say try a 300ex carb.
I’m no expert by any means, just saying what i know in the hopes it will help you.
 
  • Like
Reactions: retro
#28 ·
Thanks for you input Sam. I started very, very rich (all in my thread) and worked down from there to get where I am today (best results so far). I've always wondered about the exhaust though from day 1 issues... A 300ex has 4 valves where I have 2. So, the size potentially may play a part... I dunno...
 
  • Like
Reactions: retro
#31 ·
Just got off the phone with local atv/motorcycle salvage place. They have Moose Racing Hour/RPM spark plug meters. I'll pick one up tomorrow. Then I can start to see real world #s.
 
  • Like
Reactions: retro and SamUK
#32 ·
I've always wondered about the exhaust though from day 1 issues... A 300ex has 4 valves where I have 2. So, the size potentially may play a part... I dunno...
Bingo! Put the stock 300 pipe back on and if you see an improvement in power output while also allowing you to jet the carb for a wider, stronger powerband, you'll know that you'll either need to either change the cam, port the head, or decrease the diameter of the exhaust pipe. You can fine tune the length of the exhaust after you get the diameter correct.

Note that the word "backpressure" in the exhaust is a mis-nomer... a proper exhaust system primarily functions via sound/shock waves. Camshafts (valve timing) reinforce the exhaust scavenging, not restrictive pressures... pressures only make the exhaust quieter by limiting gross flows.

There are complicated math formulas you can use to properly predict the size the exhaust, just as there are simple equations for sizing the carb. They'll make your head hurt, but they work great...
 
#33 · (Edited)
Those little tachs work great for tuning motors! I got one for tuning my saws, lawnmower, tractor, snowmobile etc.... just move it to whatever I'm working on that day. You'll want to get one with a 0.5 second refresh rate, settable pulse per revolution of .5, 1 or 2 pulses and a MAX RPM telltale feature to tune all your small motors.
 

Attachments

#34 · (Edited)
Thanks Retro!

Insteresting.... I hooked up the compression tester. It's a UAP Napa expensive one. I turned fuel off, kill switch off. Cranked it cold. 90psi. Wouldn't hold it. It slowly dropped off. I thought the gauge hold pressure until you press button and release it. I should warm it up and see the difference.

Haha... forgot to hold throttle wide open. Battery only turned er over twice. Hit 180. Now battery won't turn er over. Stator & pick up coil must be weak...
 
#35 ·
Sounds like your battery is weak? 180 is a pretty good reading for only two pops though. If your compression tester won't hold pressure it might have something stuck in the valve. You can spray some WD-40 in the valve to help flush it out if you can reach it.
 
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