kicker
Scoot Member
Posts: 23 
Location: NZ
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Post by kicker on Sept 19, 2017 8:57:43 GMT -5
Hi all, I have a lean situation I need some help with. Here is the result of a wide open plug chop. Engine was warmed up, then new plug installed and straight to wide open for 3/4 mile then switched off.   Here are a few details Scooter was stored for 25 years before I bought it, it is unmodified as far as I can tell. It has done 2000 kilometres since new. I put a new piston in, have cleaned up the carb thoroughly. Carb is stock and has a 102 main jet, 35 pilot, float and mixture settings are as per the Honda manual. Oil pump is working and is set as per factory specs, running Motul full synthetic. I have ordered some jets for tuning in future but want to know why it is lean at factory specs first. Could this be an air leak in the crank seals from sitting for so long? I have a set on the way so will install them and see where it's at. Any ideas on what else might being going on? Thanks |
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Post by ryan_ott on Sept 19, 2017 9:12:45 GMT -5
Could be leaky crank seals due to age, but it could also be the fuel we have now isn't what it was 20 years ago and you may need to bump up the jets slightly. Is the air filter OEM and in good shape?
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kicker
Scoot Member
Posts: 23
Location: NZ
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Post by kicker on Sept 19, 2017 10:31:51 GMT -5
Air filter isn't oem but is a new replacement and oiled (finding new genuine parts is almost impossible, I'm sure they exist somewhere on a dusty shelf in the back of a Japanese dealership  ) |
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Post by gsx600racer on Sept 19, 2017 11:50:08 GMT -5
Crank seal, intake leak, cracked vacuum hose, base gasket leak, o-ring/gasket on injector pump are a few possibilities. I would get/make up a leak down tester and check for case/seal/gasket leaks for startes vs just upjetting. You will be chasing your tail tuning with larger jets if there are leaks plus it would just be a band-aid fix. Once you have verified there are no leaks then start tuning the carb.
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Post by ryan_ott on Sept 19, 2017 12:01:45 GMT -5
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Post by oldgeek on Sept 19, 2017 12:14:34 GMT -5
That Bpr6hs is a very hot heat range plug, I think a cooler plug (8?) would be appropriate. However I have no idea which plug the AF07 motor is supposed to use.  |
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kicker
Scoot Member
Posts: 23
Location: NZ
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Post by kicker on Sept 20, 2017 6:21:39 GMT -5
Crank seal, intake leak, cracked vacuum hose, base gasket leak, o-ring/gasket on injector pump are a few possibilities. I would get/make up a leak down tester and check for case/seal/gasket leaks for startes vs just upjetting. You will be chasing your tail tuning with larger jets if there are leaks plus it would just be a band-aid fix. Once you have verified there are no leaks then start tuning the carb. Cheers for the suggestions, I will check those places for leaks. I do have some parts for a leak down tester I was going to make for my RD400 but ended up going the full rebuild route so I'll dig them out and see what I can rig up. The plug is the recommended heat range but the manual does say the 4 and 8 are options if required. Would the water cooling account for the 6 rating? |
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kicker
Scoot Member
Posts: 23
Location: NZ
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Post by kicker on Nov 11, 2017 4:19:50 GMT -5
Just an update on this, I made a leak down tester a while back and found a big leak in the transmission side crank seal.
After swapping the seal out it now holds pressure, tested for 10 mins and no change.
I need to reassemble and give it a test run still.
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Post by ThaiGyro on Nov 14, 2017 4:36:07 GMT -5
That Bpr6hs is a very hot heat range plug, I think a cooler plug (8?) would be appropriate. However I have no idea which plug the AF07 motor is supposed to use.  oldgeek hit that part...your engine has very close timing to mine...(The AF01-E and TA01-E) he is correct, try a BPR7 or 8. I am in hot/humid weather and run those...never used a 6. The other items as detailed by the good minds above should be looked into first. 20 years is a long time for a seal...and it will flat spot with no crank rotation. If it runs super good with no tuning...beware! |
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kicker
Scoot Member
Posts: 23
Location: NZ
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Post by kicker on Nov 14, 2017 8:08:36 GMT -5
I'll stick with the BPR6HS for now as that is what the factory service manual recommends (it actually says BPR4 is the hot plug for this engine), daily temperatures don't get above 20 degrees at the moment and in summer we'd be lucky to see more than 25. I will keep an eye on it though and have taken the advice here onboard.
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Post by oldgeek on Nov 14, 2017 9:17:50 GMT -5
Post some pictures of your scoot if you can. We do not have those over here, it is a cool looking scoot IMO.
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Post by ThaiGyro on Nov 30, 2017 5:26:38 GMT -5
I must say...a true '83 Beat must be fun! I am guessing, since a Japan only model, that the plug recommendation had a bit to do with the V-TAC exhaust power valve and no corn in the fuel. Nice engine! 7+ hp from factory, over 35mph. We have seen a few here in Thailand. I believe the CVT is the same stepped 2 speed as our Gyro were.
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Post by eclark5483 on Nov 30, 2017 6:07:22 GMT -5
I'd like to see pictures too. The beat came stock with an expansion chamber. Cool little scooter.
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