Honda TRX300EX, Hacks for Low Compression Engine Start and Recovery!

Brought this 1998 Honda TRX300EX home last week, a dry compression test indicated a reading of 35PSI, wet compression was less than 60PSI and the engine would not start and was spitting gasoline out of the carburetor. After injecting oil onto the intake valve sealing surfaces thru the carburetor port, the engine started right up, it ran well, and there was no bad noises or oil burning smoke. Seems that the engine had an amazing recovery, I rechecked the compression after it ran for a few minutes and the reading went to 150PSI. Next video on this machine will be a drive chain install and a ride, not bad for an ATV that I almost put outback for low compression!

[@jcondon1]

Wow, that engine recovered well. Huge difference in the numbers.

[@peterzenner2020]

No kidding... 45 to 150 is really phenomenal. All with a little valve work,

[@mickreid7153]

I don't care how long you've been doing this stuff that must bring you genuine joy!

[@HarveySpooner]

Hey Mick, My joy comes in 2 flavors, the deal and then the first start, the cherry is when the engine is a diamond like this one!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@w.e.smithereens8178]

Hope I can g e t mine going like yours!

[@kentuckyyankee]

Have to admit when I saw that low compression I said dang poor Harvey!! 😂😂 Can't believe it ended up with that much compression lucky dude!!

[@michaelr1961]

Thanks for rolling the camera on your efforts/ideas to get this one popping. I have been an employed ATV mechanic for about 9 months and your videos have been a huge part of my continued employment. Just wanted to say thank you.

[@johnathanvickrey6217]

Have a 250x and been struggling to get it to regain compression after new valve seals. Your wisdom has helped a lot, now to go try your tricks.

[@peterzenner2020]

I learned a lot from this--and all your videos. Nothing is as it first seems. Nice work getting the valves to seat.

[@thevisiongetsitdone7636]

Very detailed excellent You have one of the best Atv repair videos which helps beginners being that your so instructor savy as well it’s important your very detailed

[@servingme09]

Harvey ain't no quiter. That a boy, love when you knock it out of the park.

[@kevinmccarl7405]

Thanks. Tapping the valve stems seemed to work. I never would have thought of that.

[@maxamhomerepairAndatvrepair]

Good job. YOU got her going that's a good feeling is it. I love getting Motors that set for a long time satisfying. I used to do with old cars all the time. Now I do it with ATVs.

[@dansolomon8164]

Man Harvey, that compression gauge wasn't looking good but you did it it again, you are the BoB Rose of all terrain vehicles, keep doing what you're doing, I'm near Pittsburgh PA

[@HarveySpooner]

Hey Dan, Bob Rose, the footballer? I'll take it! I almost put it in storage, I'm glad that I took the extra time with the camera running!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@martinburgess4814]

Super recovery, gotta love Honda's,

[@HarveySpooner]

Hey Martin, I love it when a vintage machine comes back to life, thanks for Ur thoughts, encouragement, watching, and commenting!!

[@aaronpowell4885]

Wow! I've had some really good "luck" along with some bad but I think that's the win of the year so far!

[@HarveySpooner]

Hey Aaron, The atv game is a game of numbers, if one buys lots of unknown junk, there maybe some diamonds or it maybe all junk, mostly, it is a mixture.... Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@aricwoods5239]

Nice man great to see them come back to life that’s something I’d be interested in for those Polaris atvs

[@dannydepino3874]

Nice score Harvey!

[@w.e.smithereens8178]

I did enjoy your video I just got one and Har no compression like 29.. gonna try what you did... thanks so much!

[@y.d.firstblood4681]

another victory for the moto maestro

[@mtec8743]

Wow that was amazing. Same thing happened to me. Exhaust value

[@HarveySpooner]

Hey Mtec! Really surprised me when it started up, even more amazing is how well it ran, now, let us hope the clutch and transmission are good! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@willtone1596]

Brought it back to life

[@mikeshobbiesandrandomstuff]

Awesome buddy I'm glad it turned out good for you 👍

[@HarveySpooner]

Hey Mike! Looks like a home run, if the clutch and trans are good, thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@schaeferslawngardenandpowe1924]

I picked up a 4x4 polaris for 400 and had it running in 15 minutes. People don't do the easy work that it needs to run.

[@joshuabowers6431]

I have a Honda 97 FourTrax then I'm going to start working on Friday it's been sitting for a couple years is my wife's and she was younger it was running a couple years ago but it was backfiring really bad after putting on a new carburetor when it didn't run before I put on the new carburetor

[@hondamanatc4life983]

Hell yeah that's awesome I have a 1991 TRX250X that I have to pull apart have to replace left side crankcase going to throw in a new timing chain while I have it apart

[@HarveySpooner]

Hey Hondaman, If the oem chain is tight, I would let it be, if it is loose, and the adjuster is approaching the end of its travel, then I would change it.... OEM Honda stuff is typically better than the aftermarket unless U buy the expensive stuff, Just my thoughts, do what U think is right for Ur motor! Thanks for Ur thoughts, info, encouragement, watching, and commenting!!!

[@nano-gq9tv]

Saved a 02 recon from a junk yard. It's my main atv now. Main thing was just carburetor on it the recons run until there locked up😂.

[@Scummy_shovel]

That little cdi hack box is pretty trick. I’m sure that comes in super handy

[@Roger-hq1yt]

I have single cylinder bike im currently bringing back to life, has only 50 psi will definitely give oiling the valve seats a go.

[@southern_merican]

did it work on yours?

[@slickricktheruler]

It’s an engine Harvey! Not a motor..... 😬 I just had to. Thanks for all your amazing content.

[@user-wj9xq7ig2v]

But why are they called motorcycles? But yup motor is electric.

[@PNWTone]

Thank you!!!

[@2strokeguru]

Awesome great job

[@Sleepy_g11]

I’ve done 2 cycles of this with the cyl, if anyone has zero compression in one cyl like I did, try atf soaking for a day if that doesn’t work out just enough atf in the cyl turn over by hand to make sure it’s not hydrolocled and start it, wait til it’s hot, then wait til it’s cold and repeat until it starts, went from zero psi to 45 consistently just waiting on it to cool for the last one or two cycles

[@futureforcaster8576]

good job!

[@HarveySpooner]

Hey FF!!! I love it when a vintage atv comes back to life!!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@AtimatikArmy]

Awesome!!

[@veggiepowered]

I'am Your Newest Subscriber Great Videos. I Need To Compression Test My 2007 Honda Rancher ATV TRX400FGA

[@troycrowder9942]

great video i do that trick it works well

[@captaindeadpool1640]

I have a 98 trx300ex it ran great my son was riding it started smoking and died. I had 10psi of compression and took the valve cover off there was some wear on the rockers and the cam humps a little wear you could fill the edge took off. Took the valves cover and you could see the blow by. It was smoking. Took off the cylinder head and the piston was shredded on the intake side . It had oil when it happened the motor was hot. Went to take of the piston and the wrist pin is siezed i am currently drilling it out on each side of the piston . It is loose through the drive shaft just locked to the piston and i took the pins out. Have you seen this before and what happened? It had set for 6 years we changed the oil got a battery and it ran the valves was loose . I had put a new oil filter in just before i quit riding and didn’t replace it wish i would have there was oil under the cam and when i took the banjo screw off oil came out so oil pump was good i guess but if you see the piston it looks like it ran dry. Just not sure.

[@JovianStone_]

@HarveySpooner When you loosened the valves and tapped them, I'm assuming you reset the valve clearance afterwards? Or would it help to turn it over while loose AF, to aid in cleaning the seat?

[@zackwhite7120]

Hey Harvey I have a atc 125m it’s has about 40 in compression on the gauge. You put oil in the cylinder would that be in the spark plug hole ?

[@johnbarker5409]

Had to tap the spark plug hole got a ton of shavings and now there’s no compression, happened once before on another bike took the head off cleaned it ran like new, is there any way to drive them out without taking the head off?

[@Vazerin]

Got a 1987 TRX250X, did a compression test and it's 125 psi and oil on plug, what do you think could be the problem?

[@jet_lif3679]

Will this work for a 2004 raptor 660 ? I can’t get mine to start 😞 I put a new starter and solenoid and spark plug and it’s just sounding like it wants to turn on but won’t . I noticed my wire harness on the solenoid keeps going out and then star buzzing sound when I try to start it and doesn’t do anything. I don’t know what else it could be if it’s the battery or something else 😞If anyone can help I would really appreciate it 🙏🏾🙏🏾

[@roberthoward5015]

Why did the gauge go up before you started turning the engine

[@junebkrkkfrk5196]

Hey Harvey I need help turning on my 110 hawk 6 I lost the keys and I can’t start it at all pls help me

[@mowersandfourwheelers5204]

I recently bought a 85 trx250 has low compression

[@larrymaykopet3365]

What was you using for the cdi box

[@willtone1596]

Hell yea

[@1drmr3]

So maybe it had a stuck piston ring from sitting too long and the oil lubricated it ?

[@reggiexp69]

oki good to know you need 50psi cause my honda trx300ex give 60 psi i tought it was low since people say 100 120 psi all quads i have give arouhnd 50-70psi max so i was confused thinking my compresion gauge was bad.. bought a 2nd one same thing... cause my banshee also just gives 50psi and wont move under its own power it starts doh no problems but wont move it dies... (i think its has some bad seals me and a friend redid the engine...)

[@jeffreyboone1909]

What type of oil did you use

[@chrissample3047]

My old boss just gave me an old 4 wheeler

[@atvseatexchange2176]

Wow!

[@HarveySpooner]

Hey Steve!!! I have that magic touch!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@atvseatexchange2176]

I jumped out of my chair when it started, and almost screamed at the compression gauge when I saw it climbing. Well done Harvey, well done.

[@atvseatexchange2176]

@@HarveySpooner I wouldn't wash those hands!

[@snoopysrc]

harvey spooner not bad at all

[@HarveySpooner]

Hey Snoopy! Sometimes I win, sometimes a have a lot of work in front of me.... This looks like a win!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@Bunkers101]

awesome, i thought it was a goner.

[@HarveySpooner]

Hey Bunkers!!! When the compression came in at 35psi, I almost put it in storage... Sometimes I win!!! Thanks for Ur thoughts, encouragement, watching, and commenting!!!

[@beans36]

I've got a 250 ex that I blew up the top end on and then replaced it all it has good compression and I recently replaced the cdi box it'll sputter but won't start any of you got any answers

[@captaindeadpool1640]

What is the cdi box? And what made you think it was that?

[@beans36]

@@captaindeadpool1640 it's one of the parts that control the electricity that goes to the spark plug and it had weak spark

[@richie8214]

Clever you am mate

[@kurtrellwynder6876]

What if it's bone dry

[@davekimbler2308]

That’s almost unbelievable in the up swing of compression , from 40 to 150 , something ain’t right ! I’m not saying you messed up at all and I did see the numbers so that leaves the compression tester equipment ! I’m wondering if you had a blockage or something and the first numbers are wrong or your gauge went haywire and your second numbers are wrong ? 110 lbs difference is HUGE ! I’m hoping that both numbers are spot on !!!!

[@HarveySpooner]

Hey Dave, I think there was stuff on the intake valve seats, remember, it was spitting out the carb, once they got sealed enough with oil it could start and once it wasrunning, the valve seats cleaned up.... Thanks for Ur thoughts, wisdom, watching, anc commenting!!

[@davekimbler2308]

@@HarveySpooner that’s as good of a theory as any ! Either way it’s up and running ! Lol

[@thulsa5218]

Toss the harbor freight compression tester in the trash. They read falsely low right out of the box. I've seen untold amounts of motors rebuilt for no reason due to a crappy compression gauge.

[@Scummy_shovel]

Those are the wrong comp testers for small engines. They will always read way lower and not even close to accurate

[@brentfellers9632]

The only MOTOR on the quad is the starter. I know your American but God man it's called an engine. Get your nomenclature straight ,you'll sound more intelligent.

[@refugeinc.159]

Not important. Everyone uses both terms.

[@brentfellers9632]

@@refugeinc.159 you need to talk the talk before you can walk the walk. Try looking it up . Totally NOT the same thing. Learn before lip

[@jlucier59]

Always the one guy

[@brentfellers9632]

@@jlucier59 who is correct.

[@whowho7969]

Even the parts shops ask what motor do you have engine. Even on quarts of oil it say motor oil . It’s ok don’t let a word ruin your day life is to short enjoy it while it last 👍