trying to go through the steps

[rbig1]

Ok I did the compression test. Low was 200 high was 210. All looked good. Switched to leak down test applied 100 psi biggest loss was 2psi. So turned pistons just over tdc pushed down on top of them no movement. Took carbs back apart no plugged jets or pilots and fuel adjustment. Am I correct the only way to change timing is tps. This rattle is like when a engine would not die on a 70s car. Just the knock part. To the point of scratching head. Enrichment valve looks fine on it also. Guess going to put it back together and check tps adjustment. Well the only good part of this is I know engine is tight now. Can rule out a lot of what ifs. Just thought about map sensor another thing to check.

[yamagrl]

Did you talk about this problem on a previous thread? It seems like I remember something similar.

[M61A1MECH]

So maybe I missed it, but what is the symptoms of the issue you are having?

When does the noise occur?

 

If it is under hard acceleration or when a load is put on in higher gears, it could be pre-detonation of the fuel. That could be caused by a few things.

1) Summer gas sometimes has a slightly lower octane rating than winter gas, I have had per-ignition knocking on my 07 in the heat of the summer months, normally a tank of mid grade gas will clear it up.

2) Could be carbon build up in the cylinders or on the heads, a small bit of red hot glowing carbon can ignite the fuel mixture before the spark plug fires, that will cause pre-detonation, normally a god dose of Seafoam or other top end cleaner will loosen the carbon and flush it out the exhaust.

 

Just a few thoughts, changing the timing would best be done using an after market ignition system like he DYNA2K that allows you program the timing as you like, but I do not think they will allow you to retard the timing, normally they are programed to advance the timing.

[bongobobny]

Hmmm, TPS would be a good "next thing to check" Rod...

[rbig1]

This has been going on since I had bike. First year I put tires lubed axles drive shift. Diamond cuts didn't plan on that. Put in muffler baffles, almost forgot clutch disc and springs, installed relay for ignition, oil change twice changed type to see if it made a difference. End of the year replaced ign with a dana 3000, new plug caps, cleaned carbs on bench replaced intake boots. Over last winter adjusted valve clearance cover gaskets new. Spring rode 400 miles decided to find problem before killing it. had the carbs off again set floats. cleaned all of the electric connectors. installed wireless puc. got mad and put stp in quieted down motor but rattle from stop take off still there for 5 feet. compression check and leak down tests completed had pan off to inspect no rods looked tweaked checked end play on crank. Looked for this gremlin every where. Did a few other things but just cosmetic. just remembered tested pick up coils and replaced back set of coils. Just cant stand that knock..... have filled 1.5 pages in repair record book. the old bike had 2.5 pages. I guess I bought bike to work on and ride 1/4 of the time. Woops forgot replaced brake shoes first year and fluids clutch and brake. Haven't tried peeing on tire yet.

[snyper316]

Haven't tried peeing on tire yet.

 

Well good ol @cowpuc talks about spitting at his cylinder heads.... Maybe you could try Peeing on them!!

[Yammer Dan]

Pee on them and get back to us.......

[Yammer Dan]

I would be shocked if it is in motor. Clutch in some way? Maybe timing chain? Starter on my 84 made a lot of weird noise and wasn't releasing just before it went. I DON'T KNOW!!!

[cowpuc]

Pull the timing plug, drop a timing light on it and see where she's hitting and how the Spark advance is performing. Pretty easy - thinking you should have an "H" stamp next to the "T-1" stamp on the flywheel (if its like the 1st Gens) - the arrow on the cover should land in between "H" arms when idling at 1 grand and the light clamped on number one plug wire.. Should get a real steady climb in the advance starting right off idle..

Actually,, I have used oil thickening products like Lucas or "motor honey" a number of times to help diagnose mysterious rattles and nocks Rodney.. Take a stethoscope or even an empty roll of paper towel to listen thru - start the motor and get er knocking - get as close the rattle area as you can pin point by listening thru the scope or tube - pull the oil fill and dump in a pint of your favorite motor quieter downer and listen closely as you add the goo.. I have rebuilt a few top ends that people have ruined by starting dry after sitting for a long time and they ruined cam journals by spinning them up with no prelube - thinking that if this is the case with your scoot, because the cam journals are part of the pressurized oil pump system it will probably quiet down fairly rapidly where gear lash rattle or a bearing that is oil bath instead of being part of the pressure system will take a little longer to quiet down.. Another thing to remember - a wrist pin rattle is unique in its location higher up in the jug and oft times will rattle at just off idle when holding a steady low speed rpm with no load on the engine. Big end bearing tend to rattle at higher r's and real noticable right when you take the load off.. As you know - ignition inspired rattles normally happen when load is applied and never affected by thickening the oil..

You ever stick an oil pressure gauge on it to see how much pressure its creating? Might not be a bad idea..

If this is happening when your riding at particular times - say like 1st gear, low r's and only as your easing away from a stop sign it could even be gear ramp up and looseness between the gears.. Clutches can rattle - does it change when you pull the clutch in? Does it lessen when you lean the bike over? Its possible that you have lost the cage on a bearing and the balls are out of sequence (all now riding together)..

Got any "buzz" in the bars when ya spin er up? Only reason I ask is I had a scoot once that I bought cheap for rebuild and resell.. Got er fired up and discovered a strange buzz in the bars and a noisy motor - got talking to the former owner and found out it had been hydrolocked = bent rod.. Talk about strange noises BUT accompanied by noteworthy vibes.. Also had an Evo Sporty that I bought dirt cheap cause it rattled and had a really strange buzz in it (Sporties have a normal low end buzz built in - this one was a nasty mid range buzz). Turned out that a PO over revved the poor thing and nocked the crank out of spec - few wacks with a lead hammer between the v-blocks pulled her back into speck and NO MORE NOISE.. Gotta imagine that nocking a crank out of spec or, being a multi pin motor - even nocking one out of phaze could cause some pretty serious rattles that should not deminish with motor honey being added..

[cowpuc]

Hmmm, TPS would be a good "next thing to check" Rod...

 

,, 2nd Gens got a Throttle Position Sensor? What da heck,, ,, is it a magnetic puc (not like me - I am a non magnetic puc) on the side of the slide body?? If so,, how can that work with vacuum operated slides.. Maybe operated off the carb that the other carbs are synced to???

Never mind,,, I'll try to keep my nose out of this and go back to 1st Gen Tech where at least I have somewhat of a clue.. I gotta get out more

[Marcarl]

The starter clutch can make such a noise. Normally that only happens when it's engaged, but weird things happen. Once the engine is running one would think that it's no longer engaged, but hey, you never know. If it's broke funny things can happen. How does the starter sound when you start it?

Just straws, grabbing at straws.

[BlueSky]

Just wild guessing here. But, 200 to 210 psig seems rather high for compression if the gauge is correct. Could the timing chain be off by one notch?

[rbig1]

Well I think I have it. The tps was .657 on low and .759 on top side. Supposed to be 650 and 750. Good enough for me. Did find the little gaskets on air box, bottom fell off so made new ones. Cleaned all the contact wire joints. Had the pilot circuit back apart but never found any problems there. Reset the pilot screws opened them 1/4 turn farther. Had my fingers on about every thing. But that is normal for me. I do know what I have now no guessing about condition. And maint is caught up on every thing except rear diff. While I was at it put winter air in tires. Exhaust notes sound smooth now. THANK YOU ALL. Maybe ill leave ya alone a while. I have only run it 20 miles....