RC390 Leaking oil from rearset throughbolt??

[samroy92]

Hey guys,

New to this forum and my RC390, it has about 7K miles on it. I just bought it and doing all the regular maintenance and noticed a small leak. It seems to come from the M10 screw bold that goes through the rearsets + frame + engine. Pictures below, any help would be greatly appreciated. I tried tightening this bolt/screw to 40 ft/lbs the manual says it should be at 36.

 

[Diploman]

Samroy, From the photos I could not spot any significant leakage. I think you may be seeing some vestiges of flung-off chain lubricant.

 

[Treachery]

Good on ya getting pics at those angles! Welcome to the forum, BTW. I'd have to agree with @Diploman. On that side in that location, with that appearance, I'm thinking chain lube too. As you'll read here, I'd be right cautious about over-torquing anything on these bikes. Be safe!

 

[Ryanthegreat1]

Looks like chain lube to me.

 

[samroy92]

Thanks for all the replies guys. I know the pictures don't capture it very well, but it is definitely leaking oil after a short ride, it drips down the side of the engine case in this picture:



The only reason you can't see it profusely is that I clean it regularly and just did a clean oil change.Still though it seems to be weeping from some point around the frame bolt (rearset through bolt). I took out the bolt and there was a bit of oil on it, but not a whole lot.

 

[Superpacman13]

What kind of chain lube do you use? Whats your oil level, is it changing? Is your chain covered in oil as well? These are all far more likely then whatever you think the cause is. Rearsets don't cause engine leakage PERIOD, its not possible.

 

[simpletty]

What kind of chain lube do you use? Whats your oil level, is it changing? Is your chain covered in oil as well? These are all far more likely then whatever you think the cause is. Rearsets don't cause engine leakage PERIOD, its not possible.

The reaerset bolt bolt goes through the engine case so it's possible It's likely the case half was not properly sealed at the factory if there is confirmed engine oi leaking. Simple test-go to local auto supply shop and buy oil leak test dye. Clean off any residual oil around the rearset or engine area that's leaking. Add the oil leak dye to the crankcase and run the engine. Get yourself a uv light and look around the engine where your oil leak is occurring. If it's glowing green under the uv light it's obvious you have an engine leak.

 

[Treachery]

^^^^^
And there you go.

 

[samroy92]

The reaerset bolt bolt goes through the engine case so it's possible It's likely the case half was not properly sealed at the factory if there is confirmed engine oi leaking. Simple test-go to local auto supply shop and buy oil leak test dye. Clean off any residual oil around the rearset or engine area that's leaking. Add the oil leak dye to the crankcase and run the engine. Get yourself a uv light and look around the engine where your oil leak is occurring. If it's glowing green under the uv light it's obvious you have an engine leak.

Thanks I will give this a shot! I am almost certain it's engine oil, question is exactly where.

 

[KTMGene390]

Hey guys,

New to this forum and my RC390, it has about 7K miles on it. I just bought it and doing all the regular maintenance and noticed a small leak. It seems to come from the M10 screw bold that goes through the rearsets + frame + engine. Pictures below, any help would be greatly appreciated. I tried tightening this bolt/screw to 40 ft/lbs the manual says it should be at 36.

View attachment 3331View attachment 3332View attachment 3333View attachment 3334View attachment 3335View attachment 3336

Check the shift shaft that goes through the engine it's most likely coming from there. This was the case on my bike with the same oil leak pattern as yours.

 

[edderz 33]

either shift shaft or sproket shaft seal burst which is quite common for RC.

 

[samroy92]

The reaerset bolt bolt goes through the engine case so it's possible It's likely the case half was not properly sealed at the factory if there is confirmed engine oi leaking. Simple test-go to local auto supply shop and buy oil leak test dye. Clean off any residual oil around the rearset or engine area that's leaking. Add the oil leak dye to the crankcase and run the engine. Get yourself a uv light and look around the engine where your oil leak is occurring. If it's glowing green under the uv light it's obvious you have an engine leak.

I finally got around to doing this, and unfortunately some bad news. I found there is a small hairline crack in the rear engine case, near the rearset through-bolt I was talking about before. The crack is about the length of a pink fingernail, and has a similar curvature.

Pictures to come... warning they are low quality because of UV light.

 

[Treachery]

Closing this thread, so discussion can continue on The new thread​.