The Hodaka Club Forum

Hey friends, Here's a Model 99 1975 Road Toad in heavy rotation as a daily rider. Oil injection is operable and in use. A slow leak has developed somewhere within the oil injection system. Tank is intact other that the typical pipe melting but no melt through. Lines are intact. Fitments were tightened and appear oil tight. I've ordered a new oil pump gasket here on SH and will change that. I don't see any evidence of a hairline fracture on the pump housing. The bike seems to be oiling properly and a bubble test confirms oil flow. I've previously used an oil additive that would fluoresce under a woods lamp to track down oil leaks in four stroke motors but I'm not sure I want to send any of that through the rest of a 2-stroke engine. Has anyone used this technique? Also, are there any locations where leaks more typically occur where I should concentrate the search? Finally, should I be running premix until this gets sorted out and is there any potential for an air leak associated with this issue in general? As always, thanks to all!

Best,

Matt

I take it you believe it's in the injection system because the "puddle" is 2 stroke oil? Where does it show itself? under the bike? on the motor itself?

Thanks, Dan. Yes, its two-stroke injector oil. Sorry, I should have been more specific. I'm using Yamalube 2S which has a green tint. I first noticed oil on the shop floor under the bike on the left side. The oil accumulates in the pump housing aft of the clutch cover and then runs out and leftward due to the tilt of the bike on the side stand.

I wouldn't run the tracer oil thru the injection system. How big a leak are we talking about? Is it enuff so you might be able to see it if you were patient and could watch it? Or is it only seen after a period of time? I'd clean the pump area, get a good light and watch it for a few mins, you might be able to see it weep out at some junction . If not walk away and check it again a short time later, like every 10 mins or so till you spot it. It may not leak where you expect, so be thorough.

Good call, Dan. I was not really cool about running the tracer through the engine anyway and you confirmed that concern. The leakage is seen after running the bike and say 3-5 ml would appear overnight, so its not a torrential leak. I'll take your advice and put it on the rack for an extended and well-lit (the bike, not me) inspection. Thanks Dan!

Best,

Matt

After cleaning it, strategically place a fresh blue shop towel under the pump with the cover off. That can help identify the source of the leak.

Will do, Dale. That's a great suggestion. Thanks!

Best,

Matt

Find out what the issue was?

Hey Dan, thanks for the follow-up. After extended observation as you suggested, I was able to locate the source in the vicinity of the pump outlet which I thought I examined well previously. I removed the pump and gave it a thorough cleaning. After that a very fine hairline crack was revealed. I was surprised that a crack that small would allow a leak to occur but there it was. I guess injector oil is thin enough to seep. Probably overtightening of the outlet fitment at some point was to blame. Fortunately, the parts stash had one to cough up so I'm back in business. I'm going to try to aluminum braze it in with a little oxy-mapp torch. I give myself a 50:50 chance of functional repair vs. total destruction but I can't stand the thought of merely tossing it. Always nice to have a spare ya know. Thanks for asking!

Best,

Matt

You keep the old one so you can show other people how small the crack can be to cause a leak.

No kidding. I could only really see it with a looking glass. Crazy!

Glad you found it Matt. I was going to offer you a pump if you didn't already say you had a spare! Let me know if the spare doesn't work. I have a total of 3 with 2 on the bikes not being used and a 3rd in a damaged case with the clutch cable mount broken. I will send it to you if you need it. ; D Victor

Very very kind offer, Victor. I installed my spare and have it set to run a bit rich for now. I'll let you know how well it works. The bubble test looked good. Thanks, Victor!

Best,

Matt

No sweat Matt. Hoping things continue to go positively for ya! ; D Victor

Us Road Toad guys gotta stick together . Thanks, Victor!