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Yamaha 30D - Hard to pull start after doing some repairs

C

Clayster

New member
Hello all. I'm new here and I am all out of idea's but i thought if anyone can help it would be here. I'll cut a long story short. I bought a second hand yam 30 about 1991 vintage, 3 cyl version. Pull start only, very basic but for my needs will do fine. I'm not a complete novice as my other boat has a Suzuki DT40 on it so i have learned much.

Anyway, I bought the engine and got her to fire up, bit smokey, didn't like idle etc but ran smooth other than that. Pull starting was quite easy. It needed work so I changed the impellar and water pump housing ( done this before) and it needed a new shift linkage aprt and engine to lower case gasket. Did all this, screwed it all back together and went to start it. VERY stiff pull start, no way can I pull hard enough to get it to fire. Pulled the plugs out and no worries, smotth, free as a bird. Trid throttle open/shut choke on/off, nothign makes much difference. removed the pull starter and thats free as a bird too. I have read about a relief valve but not sure if mine has one or even where it would be. Any help would be greatly appreciated.
 
johnnygjr said:
H??ave you looked in shop manual yet for a diagram
Click to expand...

Johnny: I don't know of any "pressure relief valve" on this engine. Do you know if this engine has pressure relief ports drilled through the cylinder walls near the exhaust ports? If so, it is possible those small relief ports have become plugged up with carbon (it is a 2-stroke 1991). If this engine has them, the exhaust cover can be removed and both the large exhaust ports and the smaller "presure relief ports" (maybe 1/4" in diameter) can be viewed and cleaned/drilled out to open them up again of those small ports are clogged up. Use care when removing all those bolts that hold the outer cover of the exhaust on not to sheer them off.

Sim Yamaha parts diagram "crankcase cylinder" exhaust cover is part # 28. Looks to be 10 bolts holding that on.
 
Last edited:
deepsea,I was referring clayster to look in manual for ideas on his issue,I was not indicating there was any pressure relief valves in my post on that engine. Sorry for the confusion.
 
johnnygjr said:
deepsea,I was referring clayster to look in manual for ideas on his issue,I was not indicating there was any pressure relief valves in my post on that engine. Sorry for the confusion.
Click to expand...

No worries. I personally don't think there is any "pressure relief valve" on that engine. I'm betting it has a small pressure release port drilled in each cylinder near the main exhaust ports. Those small ports serve to reduce compression pressure at lower turnover/cranking RPM and provide some relief for easier pull starting. If it was an old engine and he got it to fire and it smoked alot perhaps he brioke lose some carbon that caused one or more of those ports that may have been 80 or 90% clogged to clog 100%. I looked at the schematics and didn't see any ports drawn on them from the angle of the schematic but that doesn't mean they aren't there. I recommend he contact Sim Yamaha and ask of that engine has pressure relief ports in addition to the main exhaust ports before wrenching that far into it to see for himself... Then again, if he has the time there's no better way to figure out an engien than to start taking it apart!
 
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