350X refresh questions

[rot box]

Hey fellas, Our 85 350X that my dad bought new has been a dune machine for as long as I can remember. No clue on hours but this engine has never been opened up—ever. Still runs like new no issues to report. This winter I’m going to give it a frame gusset kit (much needed) and I’d like to freshen up the top end. What can I do to give it a little more giddyup?? I ride it twice a year at St. Anthony other than that it sits. Was thinking a wiseco 10.5:1 piston and a cam would wake it up a bit? What should I replace or inspect while I’m in there?

Thanks for any help,

Andrew

[Shawn Powell]

Hey fellas, Our 85 350X that my dad bought new has been a dune machine for as long as I can remember. No clue on hours but this engine has never been opened up—ever. Still runs like new no issues to report. This winter I’m going to give it a frame gusset kit (much needed) and I’d like to freshen up the top end. What can I do to give it a little more giddyup?? I ride it twice a year at St. Anthony other than that it sits. Was thinking a wiseco 10.5:1 piston and a cam would wake it up a bit? What should I replace or inspect while I’m in there?

Thanks for any help,

Andrew

If you’re gonna do the piston go with the 12-1 , Webb cam , 400ex carb and a good exhaust (HRE header with a 450r muffler) and port then head if you have the money or know how. This will give you a real reliable machine and really liven up your experience. Of course this gets pricey , I would for sure do the 400ex carb you could get a used one on eBay (you’ll need a 400ex throttle cable as well) and while you have it apart get an EBC heavy duty clutch kit for a 300ex


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[rot box]

Thanks for the reply Shawn, would a 12:1 require race fuel? Was kinda hoping to keep her on 91.

[Shawn Powell]

Thanks for the reply Shawn, would a 12:1 require race fuel? Was kinda hoping to keep her on 91.

Depends on conditions. If that’s real concern then use the 10.5-1. My bike will run on 91 if it has to but I wouldn’t run it hard or dune ride like that. When I go to the sand once a year for the invasion I run pure unleaded 108 VP. Most of the time I mix it 50/50 with 91. (100 octane) and it runs great. Keep in mind most of your modern efi 450/250/‘s run on 91 and have 14-1 comp. Granted they are water cooled and the efi compensates for fuel / air ratios depending on exhaust temp / and humidity all that fancy stuff. Higher octanes in a high comp air cooled bike will help keep it cooler. This is what I was told by the guys at racetech who did my machine work / head porting. I guess it just depends on how much power you wanna squeeeze out of it.


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[rot box]

Thanks again man I appreciate the help.

[BOB MARLIN]

I run all my 350’s with a 10.25:1 wiseco. They run better than stock, start better and it seems to add a bit of torque. Plus they really don’t care what fuel you run. Add an old supertrapp exhaust and you’ll have a real nice running very dependable machine. If you want real HP gains you’ll have to go with what Shawn suggested.

[rot box]

Thanks for the reply Bob, speaking of exhaust I currently have a Cobra and it is too LOUD! I’m thinking (if I can’t track down a supertrap) I’ll cobble together a 450 muffler. Anyone know what years work best? Looking for one with a spark arrestor...

[BOB MARLIN]

Ya, the cobras were kinda loud. I have a nice DG on one of mine but the thing is so loud my ears ring after a long ride.
Someone will chime in on the 450 muff. I have no experience with that, but I know it’s been done .

[Shawn Powell]

Contact HRE atv , I believe they are in Pennsylvania, they make and sell a header that will work with any modern (2008ish) 450r TRX muffler. Stock or aftermarket. I used a Lexx from rocky mountain atv. Comes with a spark arrestor and a quiet core. Up to you , I’m running just the arrestor but it sounds great. You can always find an eBay stock muffler I’m sure.


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[rot box]

Thanks fellas, a Lexx would be perfect! I’ve ran them on dirtbikes in the past great results.

I’m going to start pulling it down soon. It’ll mostly be a winter project looking forward to breathing new life into the ol’ girl.

[Shawn Powell]

Thanks fellas, a Lexx would be perfect! I’ve ran them on dirtbikes in the past great results.

I’m going to start pulling it down soon. It’ll mostly be a winter project looking forward to breathing new life into the ol’ girl.

Make sure when you order it get a later model I think 08 and up other wise you’ll get the wrong gasket. Easy fix and Rocky Mountain sent me one free of charge but takes time. Talk to the HRE guys they know what year to order.


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[6spdls1z28]

I have a 400ex big gun silencer on mine with a custom head pipe. I put it on YouTube how it was made.

[rot box]

Thanks again fellas

[weird350x]

I have a 400ex big gun silencer on mine with a custom head pipe. I put it on YouTube how it was made.

link to the build?

[Dirtcrasher]

The OEM stock TRX450 muffler was a nice upgrade, but it wasn't doing you any favors in performance and it's large and heavy. Honda used to off an HRC tip for that exhaust, I still have one. It replaced the stock tip and put a much larger diameter tip on there. If you can find a DG head pipe (they seem to be about the biggest diameter), but if I recall, the Cobra headpipe may have been a fairly large diameter as well. Unless someone just but a Cobra onto the OEM head pipe? If you find a DG headpipe, then you can mate it to a better flowing, lighter silencer. Like the Big Gun mentioned above, a Supertrapp, a Yoshi, or any other exhaust used on the TRX 450R. If your head flows well it has to get out of the exhaust well too.