Sounds to me like air sucking through a small opening when kicking it. If you don't have a mechanic's stethoscope, use a long screwdriver with your ear on the handle to probe for sound location as it runs.

That first vid where you are simply kicking does not sound good.

Renegade578,

I agree with WFOPETE 

That doesn't sound good at all. Sounds like something rubbing metal to metal. I would not run the engine again until you find and fix the noise problem. You have 2 many things going on here. I know its hard sometimes when your not a experienced tech but stick with one issue at a time. Don't assume anything. eliminate one problem at a time.

If that loud noise while kicking it over started immediately after installing the different style crank seal that you now say sticks out 3/32 from the crankcase, then go right back in there and take it out. Then kick the engine over with no seal and see if noise goes away. Look carefully at the seal and bearing. See if it was rubbing, see if the inner seal lip spring came off and went into the bearing. See if you had the seal in backwards? Easy to do on that style seal. Measure how far the bearing is in compared to crankcase seal edge. There should be room between seal and bearing with seal flush on case edge.  Measure the seal thickness. You do not want the seal rubbing against the bearing. It's not possible on my DT250's because there is a circlip between the crank seal and bearings on that engine. Not so on your engine. It's the easiest and most logical place to start since you say your noise started immediately after you installed it.

If nothing is found then install the original design seal you got with your kit and see how if fits in the case. Put a slight film of oil or silicone spray on the seal lip that rides on the crankshaft. don't over do it. Nothing on the outside. Make sure everything is clean. Carefully start the seal flush in the engine case with your hand and use a small pc of wood 2 or 3 inches wide 1/2 or 1 inch thick and about 6 to 8 inches long and carefully knock it in on 3 sides of the seal by hammering on the wood lightly. I don't like using sockets to drive seals in unless there a perfect fit on the outer edge. If not it can damage the seal. 

Fixed or not, at least you eliminated the left crank seal as being a problem and you can move on. It won't take you long to do. It's a easy check and fix.  

Here is a picture of RT360 engine crank seal installed if that helps. 



 

Just read your entire thread and I have questions. Did this bike run at all when you got it? What is the history of the bike? Did you get it in a basket already torn down? If so are you sure all the CORECT parts were with it? You say there was water/rust in the flywheel side of the cover. Was the bike under water or sit outside in the weather for extended time? Did you have a good manual to reference while doing the work? You said you did a "Total restoration" and replaced all the bearings and seals. Does that mean crankshaft and rod bearings too? If you replaced the crank bearings you would have to split the cases to remove the crankshaft. Who checked the crankshaft and connecting rod for excess clearance and was the connecting rod or rod bearing replaced? I say all this because you are dealing with a 40+ year old bike that was likely beat on by someone at some point and a lot can go wrong or be worn out. The good news is in many ways these bikes were built like tanks and can take a beating but we all have our limits.

I don't mean to be a **** but if you missed installing a crank seal what else did you get wrong? And full disclosure here; I just got finished rebuilding a 78 DT175 and I had several "DUH" moments during the rebuild; including installing the primary gear backwards. One thing I did during my rebuild was to rotate the engine after any major component was installed to see if there was any binding or unusual noise. I hope to start it in a few days so I may be in for some rude awakenings too.

All that said, if it were my bike I would start by pulling the clutch and ignition covers, remove the sparkplug and rotate the engine by both hand and the kickstarter. Try to locate the noise and/or binding and check both sides.  Check for up/down movement of the crankshaft too while you are there. I suspect a "Clutch Side" problem but it's just a outside guess so don't ruling out anything. Beside what has already been talked, I would remove the clutch assembly carefully looking for shiny spots or other indicators of where metal-to-metal contact was made. There are several "Thrust" washers in the clutch assembly; leaving one out or installing them incorrectly will cause wear and/or binding issues. Check the alignment of the parts as they go together. If something doesn't look right; it probably not right. Again a good manual will go a long way in helping.

I was planning on removing the crank seal and investigating from there as my next step. I might have time to work on it tomorrow. The history of the bike can be found here:

yamaha-enduros.com/index.php/forums/rest...75-dt175-restoration

I’m aware that if I missed the crank seal, there are other things I could have missed too. I took a lot of pictures during disassembly and made sure everything moved smoothly as I reassembled it, referring to diagrams from repair manuals every step of the way. I’ll let you guys know what I find when I pull the crank seal.

Good luck on finding the issue Renegade, I hope it's something simple.

That was a good read.

Crank shim(s) missing? 

I think that all of the advice is good
just my opinion, but i would take it all back apart and then put every component back together using the exploded parts breakdown on partzilla as the guide.  Every part in its place, then nothing can go wrong, right?  Then set the timing.  Then blow the crap out of the carb one more time, putting a fine copper wire down and across the pilot jet.  Then set the timing.  Then it starts and you go for the most satisfying ride!

Listened with headphones on & i don't know. Motor looks like it has full compression watching kicking so not a 'ring thing'. If crank shim on the right was missing i don't really think crank lightly rubbing on the case would make a noise like you say. Seals must be good as motor sounds healthy & rich. If a seal was in too deep & touching the cage i still can't imagine a noise. How about kick gear not fully clearing the idler intermediate gear. You'd feel that manipulating the kick lever when running. I can't get a good earful of anything definitive & just a lot of general noise. Not baffle plates in the exhaust come unstuck & rattling. This isn't an option i know but be good if you could rope start it around flywheel with clutch removed so nothing is turning in the transmission. Actually a good torquee drill might start it & i've done that on 100-125's come to think but 175 has plenty of comp to force through. Wouldn't hurt running with clutch cover off & clutch basket removed. Need a super tight mag nut but drill isn't a hammer drill just a torquee drill. Ok silly ideas over lol.