TRX300 Carb Rebuild

7819 Views 36 Replies 9 Participants Last post by Goober, Apr 25, 2019

Goober

Discussion Starter · Mar 15, 2018

I bought a junked VE90E today as a rebuild project. The carb on my 93 is a bit temperamental after 25 years—it needs a cleaning but I wanted one to swap out with it. So $24 wasn’t a bad deal.

I’ve never rebuilt one of these but looks simple enough. First thing I did was soak it down with some deep creep. Maybe tomorrow night I’ll wipe it down and start breaking loose the screws. I have a Shindy gasket kit on the way.

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fishfiles

· #2 · Mar 15, 2018 (Edited)

I may be wrong , but looking at my list of carbs for the different years of the 300 , I think the 93 carb is a VE90A , not a VE90E , don't know if it makes a difference , maybe as simple as jets are different ----I like Deep Creep by Sea Foam , good stuff !

Oh , the VE90E doesn't show to fit any year 300 , I have the VE #'s from 91-2000 , I don't have the numbers for 88-90 , it might be one of those years , I do know the 88 was by itself and the 89-90 are the same carb

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Goober

Discussion Starter · #3 · Mar 16, 2018 (Edited)

3

Thanks FF. My manual says it should be the right one.
It’s stamped VE90Eagg and mine
Is stamped VE90Eagk so I’m thinking it’s an older carb.

I got it completely disassembled; it was very dirty but not too badly stained or worn. The bowl seal was crispy and there was backfire soot in the carb throat! Sofar I’ve only used hot water and Dawn dish soap

I found the pilot jet was incorrectly with no washer under the oring. The primer bulb was also crumbled.

I may have questions about the plugs and passages on this unit but only after I review the manual

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retro

· #4 · Mar 16, 2018

I sensed that a potential sticky may be blooming since your 1st post Goober. Forewarned is fair-warned, no?

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SamUK

· #5 · Mar 16, 2018

One difference I knownof between early and later carbs is the choke plunger, the earlier carbs had a shorter, larger diameter plunger whereas the later variant had a longer, smaller diameter plunger.

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Goober

Discussion Starter · #6 · Mar 16, 2018

retro said:
I sensed that a potential sticky may be blooming since your 1st post Goober. Forewarned is fair-warned, no?

I like the sticky the FlyingW posted on the trike site! I will look at the stickies we have here as I’m sure the more established members may already have one. Maybe not specifically for VE90 carbs. I can’t go as in depth as him (yet), maybe share some cleaning techniques and learn others. Like his lesson on media blasting was excellent

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Goober

Discussion Starter · #7 · Mar 16, 2018

SamUK said:
One difference I knownof between early and later carbs is the choke plunger, the earlier carbs had a shorter, larger diameter plunger whereas the later variant had a longer, smaller diameter plunger.

Thanks Sam great point! I wanna know how that sucker works; I see passages that are drilled and plugged in the bowl, leading to the carb body. So after I study the principles of operation I may come back to the members for some questions about the priming feature.

Goober

Discussion Starter · #8 · Mar 17, 2018

3

Got my carb kit and Parts ready for cleaning. I usually use Berryman Chemtool carb cleaner but they were out so I picked up Berryman Chemtool fuel injector cleaner. It worked great on the bowl. I want to soak the body but not in the same solvent I used for the bowl. Wow dissolving the stains instantly!

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Goober

Discussion Starter · #9 · Mar 17, 2018

All done cleaning this carb except for blowing out the remaining small passages. A few conditions that might have led to the owner parting out this quad:

Carb was very dirty
Carbon deposits in throat (scorched)
Primer bulb diaphragm was crumbled
Starter valve oring worn smooth
Starter circuit plug missing
Pilot jet missing the washer under the oring

misterclean59

· #10 · Mar 17, 2018

Goober, one minor correction. that is the fuel screw not the pilot jet. The pilot jet is next to the main jet inside the float chamber. Hope this helps bro

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SamUK

· #11 · Mar 17, 2018

I think goober is referring the the ‘needle jet’ operated via the diaphragm. The pilot adjusts air/fuel mixture.
Pretty sure I’m right, I’ll happily stand corrected though lol

retro

· #12 · Mar 17, 2018

Congrats Goober, that $24 carb turned out to be a very useful bargain! Great work!

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SamUK

· #13 · Mar 19, 2018

Something that caught my attention...

I see some of the guys that are mad into tuning and mudding are drilling the slide in the carb, a 1/8” hole, I don’t know where, I have asked the question though. @retro I’m sure you may know the answer to this?

They say it improves throttle response and 90% of the guys who are doing this donit when snorkelling.

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retro

· #14 · Mar 19, 2018 (Edited)

Oh my, its been quite a while since I seen that done! Thats an old-school mod that helps old hollow slide Mikuni carbs respond off-idle when giving it the throttle. They used to drill a tiny hole just above the bottom edge of the slide, centered on the inside wall of the slide. The reason for that was those old slides were hollow. The wedge shaped cutout (on the atmospheric pressure side of the slide) was very shallowly cut at the factory. Folks tried cutting them at different angles and achieved some small power gains at WOT, but in doing so the bottom end off-idle response suffered due to loss of a strong pressure/velocity signal that those factory shallowly cut wedge angles provided. So they drilled small holes in the back wall of the slide to help compensate for velocity losses. It served to mix & atomize fuel a bit better at low RPMs perhaps, but other than that it was just a bandaid. Later on Mikuni started providing flat-slide carbs for factory racing bikes and those hollow slide mods disappeared.

EDIT:
Basically what they were doing was modifying the venturi shape (provided by the cutout angle in the slide) for maximum flow, then when they noticed the bottom end wasn't working they drilled a hole to provide for a "leaky" venturi. I think the idea was based on the assumption that once a small column of air is set in motion it takes less time and energy to accelerate it as the venturi volume is expanded by throttle opening. Something like that...

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retro

· #15 · Mar 19, 2018

Snorkeling is a science all by itself. A design project unique to every application. Four-strokes are much more sensitive and more vulnerable to sudden changes in air mass density and velocity in a confined length of pipe than a two-stroke is, because the intake stroke happens only once every two revolutions of the crank. A single cylinder four-stroke is the worst possible candidate for a snorkel that I can think of. I'd avoid them wherever possible. If not possible to avoid, then make them as short as possible.

A snorkel can be used to provide great advantage if carefully designed and refined, but in general practice they commonly aren't. I'm sure most Honda ATVs that receive snorkels suffer through most of the RPM range, with a few rare exceptions scattered here and there. It sure would be nice if one of you guys would write some software to help everyone begin with a sound baseline snorkel design... start a thread.

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fishfiles

· #16 · Mar 19, 2018

Retro , hit the nail on the head about snorkels , they do effect the performance , some makes and models more than others , Yamaha seems to me the hardest to fine tune after snorkeling --------personally I feel lucky as I have 5 atv's with snorkels , 4 300's and a 450 and all were no real problem

I remember when I tried to snorkel my Bronco , that didn't work out too good for me at all , first I ran 4 inch pvc pipe up along the window post to the roof , drilled holes for screws for the clamps into the post and cut a hole thru my fender , stupid is as stupid does , it effected performance bad and I never could get it right , then someone tells me to run the tubing into the cab , that was a mistake , even though it ran better with a shorter tube , I was getting gas fumes in the truck and your eyes would burn

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SamUK

· #17 · Mar 19, 2018

retro said:
Snorkeling is a science all by itself. A design project unique to every application. Four-strokes are much more sensitive and more vulnerable to sudden changes in air mass density and velocity in a confined length of pipe than a two-stroke is, because the intake stroke happens only once every two revolutions of the crank. A single cylinder four-stroke is the worst possible candidate for a snorkel that I can think of. I'd avoid them wherever possible. If not possible to avoid, then make them as short as possible.

A snorkel can be used to provide great advantage if carefully designed and refined, but in general practice they commonly aren't. I'm sure most Honda ATVs that receive snorkels suffer through most of the RPM range, with a few rare exceptions scattered here and there. It sure would be nice if one of you guys would write some software to help everyone begin with a sound baseline snorkel design... start a thread.

So I’m your opinion drilling a hole in the slide will have little affect if any at all?

I may just do a thread on snorkelling, not until I have mine set up/fuelling properly though. Be a couple of months I’d have thought.
I plan on making an airbox at some point to, seems the hardest part to keep sealed is the joint to the airbox, if I can make a steel airbox I can jubilee clip the hose directly to it and eliminate the weak link.
As far as I know I just need to cut the airflow slightly, I have a 1 1/2 to 1 1/4 reducer I plan on trying in the end of the snorkel, I’m sure it only needs the slightest amount, I’m really close.
Have to wait and see!

fishfiles

· #18 · Mar 19, 2018

Sam , you have a 300 , are you sure the snorkel is your problem , did you ever try a new OEM carb on your bike ? ----------------- on my 300's , all 4 that are snorkeled run 1 1/2 pipe , no reduction in pipe size , except for going in the air box , there at the air box it is a 1 1/4 piece of pipe , they all run great and I never have all the swopping jets or tampering with orifices in the air tubes -------- if you seal the top of the air box lid with aquarium grade clear silicone and let it dry over night before you snap the lid down , it does a very good job of sealing out the water , if after opening and closing the box 6 or 8 or a dozen times the silicone starts getting messed up , then that silicone comes off easy and do it again , leaning it over too far or flipping it , is the way water gets into mine

SamUK

· #19 · Mar 19, 2018

I’ve considered swapping the carbs over but they just cost so much this side of the pond, hence me persevering with the one I have. I do have 5 to 6 inches of the 1 1/4 pipe from the airbox then straight into 1 1/2” all the way.
Making an airbox was just something to do if I’m honest, I enjoy engineering projects, I haven’t had a leak myself as yet (fingers crossed) and I’ve beem that deep I lost sight of the handle bars!
What kind of prices are OEM carbs over your way?

fishfiles

· #20 · Mar 19, 2018

96 up , new Partzilla $245

https://www.partzilla.com/product/honda/16100-HM5-L01?ref=2e9a443095f7f5364a9afa00df1935332aac8770

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