GT186 manifold - carb fouling engine mount

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vegansydney
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I'm the final stages of an GT186 build and have discovered that the carb, a Mikuni TM24, won't fit as it fouls the engine mounts. I found it strange because the GT Assembly Manual specifically mentions the TM24 and suggests 'ballpark' jetting. Searching the archives here also suggests that a number of others are also using this combo.

To complicate the issue further, there appears to be two versions of the 25mm Gran Turismo manifold. Mine is the later version that is upswept.

Since discovering the issue, I've also spoken an experienced builder and they confirmed that in the past they've cut the 25mm manifold and re-welded it at a more accommodating angle so the TM24 clears the mount. I'm willing to go down this route (and change it to a flange type mount while at it), but seeking advice from others running a TM24 on at GT186 first. Thanks!
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coaster
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I cant be sure about the 186 but there are two manifolds available for thr 200 and 240 depending on which side you want to mount ther carb. I also believer that its possible to mount the manifold either way as the mount is symetrical. Is it possible you are using the wrong manifold or have it the wrong way round for your application?
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vegansydney
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Thanks for the suggestions! Appreciate it.

The manifold is 25mm, I double checked it with calipers, and the TM24 fouls the engine mount, regardless if the manifold is facing the flywheel or kickstart.

Curious how others have managed to fit the TM24 to a GT186.
Adam_Winstone
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A friend has recently found the same with a 25mm PHBL, which is just touching the mount.
Grumpy225
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I did this years ago. The plan was to have a new manifold cast but I never got around to it.

Image

it worked pretty well and only slightly kicked the air boot out when using an air box.
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Rich_T
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The GT manifolds are symmetrical but that doesn't mean they fit properly when rotated around. The general advice is fit them the way there are designed for. The TM24 is popular in USA but other than some reports on the jetting I don't know how they went about clearance issues, the first manifolds did need a modification and judging by the picture above the new versions still need a bit of an adjustment. Even with a PHBL25 the over-flow elbow closest to the mount has to be removed.
storkfoot
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Damn. This was going to be my next build. I love the TM24, as it is such a responsive little carb, and wanted it on the GT186.

I have another GT186 with 115 conrod and 8mm packer. Does anyone think this would allow it to clear the mount?
Grumpy225
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Rich_T wrote: Mon Nov 18, 2019 7:34 pm The GT manifolds are symmetrical but that doesn't mean they fit properly when rotated around. The general advice is fit them the way there are designed for. The TM24 is popular in USA but other than some reports on the jetting I don't know how they went about clearance issues, the first manifolds did need a modification and judging by the picture above the new versions still need a bit of an adjustment. Even with a PHBL25 the over-flow elbow closest to the mount has to be removed.
The photo is from a very early kit. Not sure what has changed with the newer ones. If I can find my notes on it I'll post the amount of angle change that was needed.
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vegansydney
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storkfoot wrote: Mon Nov 18, 2019 8:41 pm I love the TM24, as it is such a responsive little carb, and wanted it on the GT186.

I have another GT186 with 115 conrod and 8mm packer. Does anyone think this would allow it to clear the mount?
I agree. It's a fantastic little carb, and far superior to the PHBL. An 8mm packer might give it sufficient room. Some quick, 'back of napkin' calculations suggest the carb needs to move at least ~6.5mm forward to clear the mount.
storkfoot
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vegansydney wrote: Mon Nov 18, 2019 10:03 pm
storkfoot wrote: Mon Nov 18, 2019 8:41 pm I love the TM24, as it is such a responsive little carb, and wanted it on the GT186.

I have another GT186 with 115 conrod and 8mm packer. Does anyone think this would allow it to clear the mount?
I agree. It's a fantastic little carb, and far superior to the PHBL. An 8mm packer might give it sufficient room. Some quick, 'back of napkin' calculations suggest the carb needs to move at least ~6.5mm forward to clear the mount.
Cheers for that, VS. I wasn’t planning on using an RD400 Conrod on this build and I may well go for a cut and weld resolution to the problem but 6.5mm isn’t too far out.

There’s always offset mounts, I suppose, but my previous attempt with them wasn’t entirely successful. That said , don’t Rimini do a fixed offset set up?
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