Tomos engine rattle

roy jongejan /
anderew
Jul 19, 2020 03:11PM

Okay so I have this weird engine rattle that only occurs when the engine is hot, and nearing top speed or closing the throttle slightly to maintain speed.

Does anyone have an idea what it might be? I'm guessing possible engime knock myself.

Setup: 15.15 SHA with a 66 jet, short intake manifold, 65cc airsal kit, machined down 65cc cylinder head for higher compression (185 psi compression), and a basic but wide exhaust to match the cylinder.

It does a nice 35mph with my weight on it and rides smoothly, apart from this dang rattle!

IMG-20200517-WA0001.jpeg
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Re: Tomos engine rattle

Tri-ped Dave O.D.B. /
chefhockey
Jul 19, 2020 03:33PM

Diagnosing a noise without hearing it is basically impossible, but I have never met a Tomos that doesn't make noises.

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Re: Tomos engine rattle

roy jongejan /
anderew
Jul 19, 2020 04:02PM

alright i can make a video, but not sure on how to share it

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Re: Tomos engine rattle

P D /
pdcomm
Jul 19, 2020 04:20PM

> roy jongejan Wrote:

> -------------------------------------------------------

> alright i can make a video, but not sure on how to share it

Host the video on YouTube . Then post the link here , using the little black movie tape icon above the reply box .

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Re: Tomos engine rattle

roy jongejan /
anderew
Jul 19, 2020 04:28PM

here it is

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Re: Tomos engine rattle

Hepatitis J [OFMC] /
johneaaron
Jul 19, 2020 05:36PM

Sounds like pinging to me. Are you running a head gasket?

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Re: Tomos engine rattle

roy jongejan /
anderew
Jul 19, 2020 05:52PM

2 actually, might have been a little too ambitious on the lathe, like I stated the head has been machined down to achieve a compression of 185 psi/ 13 bar, not sure if this is too much or not

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Re: Tomos engine rattle

Hepatitis J [OFMC] /
johneaaron
Jul 19, 2020 06:02PM

Yeah dude that's really high

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Re: Tomos engine rattle

roy jongejan /
anderew
Jul 19, 2020 06:09PM

I see.. well time for a new head then i guess, what would be a good /normal/ compression?

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Re: Tomos engine rattle

Hepatitis J [OFMC] /
johneaaron
Jul 19, 2020 07:28PM

It may not necessarily be too high but it's pretty high. What's your squish look like?

You can try to retard your timing a bit to compensate but since you freely admit to maybe going to far with the lathe I'm going to lean that way too. You won't be able to lower your compression with base gaskets without messing with your port timing. Check your squish and the thickness of your head gaskets. If they're the thinner .2mm type maybe you can stack two thicker ones.

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Re: Tomos engine rattle

The Dude /
adventurewagen
Jul 19, 2020 07:43PM

Stock crank?

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Re: Tomos engine rattle

roy jongejan /
anderew
Jul 20, 2020 05:34AM

nah I put a TopRacing crankshaft in there.

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