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Daniel Palmer

DR350S bottom end rebuild kits?

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Hello all. I am a new member and a long time reader of your forums. I recently came into possession of two 1991 DR350S. The first bike shown runs, is plated, and needs just your basic ergonomics upgrades. The PO says he put a brand new top end into it. When I checked the oil it was practically brand new(and didn’t smell like gas). It started on the fifth kick after sitting for a few months. He is a good friend of mine so I trust he is not yanking my chain. He also says it slips in 5th, so I will do a clutch. And while I am in there I will check the notorious shift drum bolt, and clutch spacer washers. Seemed to shift fine. Cold and warm. Also will do the Pumper carb and Airbox mods. Also a suspension rebuild is in the plans once it’s up to snuff. I am not complaining for $500. Anything else I should check? 7B4E0406-CE27-4FEB-AA61-FC2C959EA581.jpeg.6d594d76c3f6fd04b6ed0325b413cae9.jpeg

The second bike shown is just a parts bike I got for an extra couple hundred bucks. Basically just got it for the motor. The odometer says it has just under 25,000 miles on it. I was planning on rebuilding it, and putting a 440 big bore kit in it to swap into my street legal DR. I have scavenged the Internet the past few days, but I cannot find a specific bottom end rebuild kit for it. I can find top end kits all day, but I’m going to put a big bore kit it anyways. My question to you guys is am I going to have to scavenge through OEM parts lists and order every single part individually? Or do you guys know of someone who has bottom end kits available? I know they are old bikes, and parts for them are getting harder and harder to find. I would just like to make sure the bottom end is all ready to go before I add more compression and horsepower. I learned the hard way back in high school when I bored my old XR250 into a 280. The counter shaft proceeded to shear in half 3 1/2 hours in, consequently seizing the motor and eating the bearing race in the case. Rendering it a pile of metal. Any help and or ideas would be greatly appreciated. These old air cooled bikes are not the fastest. But they sound great, and run forever. 

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the short answer is yes, OEM parts is your best bet.

even back when they were new i dont recall there being upgraded rods or crank kits for the 350. Plenty of big bore 385 and 440 just run ok with stock bottom ends. 

nowadays not much options other than go with an OEM rod kit and install it on your old crank which is quite durable.

if you find an upgraded rod i will love to hear. sadly, i dont think there is one.

last tip, head over to the dr350 thread in ADVrider forum, much more people who are into tuning there motors over there.


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I was mainly looking for OEM. I just want to freshen up my bottom end to be better able to handle the higher performance of the big bore kit. I was just mainly looking for the convenience of a bottom end kit to ensure that everything that needs replacing gets replaced. I’ll keep digging and check out some local dealers on parts. Thanks for the response I appreciate it.

Good to hear the bottom ends on these bikes are durable. Makes sense that most of the threads are on top end rebuilds.

Who knows when I split the cases everything will be fine. 25k on these motors isn’t much. If the PO did his/her due diligence. 

I have read the ADVrider forums. Maybe there are some I missed. There is a lot of good info on there. 

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