Has anyone installed thicker engine bolts on their Grom Clone?

derekracer · 08-29-2022, 06:15 PM

I'm in the process of upgrading the stock M8's to M10's. Interested in anyone's experience. I have purchased Grade 11.9 M10x1.5x120mm bolts. Just waiting for my metric drill bits to come in the mail.

TominMO · 08-29-2022, 07:02 PM

I doubt that you need thicker, just higher grade. I know that a few years ago there was a problem with one of the Grom clones, maybe the Vader, having too weak engine mount bolts that broke. But they upgraded theirs too. I would think Grade 8 bolts will be fine. Find out what they use on actual Groms.

derekracer · 08-29-2022, 07:45 PM

I am indeed upgrading them to 10 for the purpose of reducing vibration. There's to much wiggle room on the tunnel portion going through the engine with the stock 8mm bolts. I'm pretty sure the engine is drilled out for 10mm.

TominMO · 08-29-2022, 09:59 PM

OK. So the motor will take 10mm bolts, or the tunnel needs to be slightly enlarged to do so? Or just the mounts need to be opened up?

Big Bird · 08-30-2022, 09:43 PM

Yes many people drill the mounts for the next size up standard or metric bolt. Lately it's been popular to get the aluminum aftermarket bottom mount for a grom and drill holes to match up to the china engines. Typically called the "3rd mount" mod.

Grom has 3 mounting points with 10mm bolts from the factory.

Even though the clones come with "12.9" stamped bolts they are still garbage that snap.

Deckard_Cain · 08-31-2022, 09:10 AM

Quote:

Originally Posted by TominMO

I doubt that you need thicker, just higher grade. I know that a few years ago there was a problem with one of the Grom clones, maybe the Vader, having too weak engine mount bolts that broke. But they upgraded theirs too. I would think Grade 8 bolts will be fine. Find out what they use on actual Groms.

I think that was the Hellcat, specifically... but they're all basically in the same boat; just the Hellcat's were particularly bad.

TominMO · 08-31-2022, 09:35 AM

Quote:

Originally Posted by Deckard_Cain

I think that was the Hellcat, specifically... but they're all basically in the same boat; just the Hellcat's were particularly bad.

Right, it was the Hellcat I heard about on YT.

CheapThrills · 08-31-2022, 04:26 PM

Anyone have the actual steps to replacing and increasing the size of bolts?

Like drill out with XXmm drill.

Replace bolts with xxmm x xxmm & xxmm x xxmm?

Thx,

P.S. Haven't increased the engine mount bolts yet, but fixed my recently broken one and remaining stock one with some bolts I bought at the hardware store. Back to riding and now I can take time to properly look into mod'ing the frame for larger bolts. https://mymotorcycleblog.com/boom-va...olts-replaced/

derekracer · 08-31-2022, 08:22 PM

I currently have 10mm bolts in my possession. I have a 10mm drill bit coming in the mail tomorrow. I hit the frame holes with a 3/8 drill bit (close enough to 10mm hoping the bolt would slide right through. From my research the engine should have a 10mm tunnel running through it and hoping no drilling of engine hole required. I had a very difficult time aligning the 3 holes back together even with a floor jack so I put it on the backburner until this weekend. I will drill out the engine hole if need be though. Ill let you guys know how it goes and what was required.

ripcuda · 09-07-2022, 04:06 PM

I had an engine bolt break on my Hellcat. Resolved this with new 5/16" x 5" (long) Grade 8 bolts from the hardware store. I also welded up an under-engine 3rd mount. No issues since. Pics in the thread linked in my signature. GL.

08-29-2022, 06:15 PM	#1
derekracer Join Date: Aug 2022 Posts: 3	Has anyone installed thicker engine bolts on their Grom Clone? I'm in the process of upgrading the stock M8's to M10's. Interested in anyone's experience. I have purchased Grade 11.9 M10x1.5x120mm bolts. Just waiting for my metric drill bits to come in the mail.
	0

08-29-2022, 07:02 PM	#2
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,868	I doubt that you need thicker, just higher grade. I know that a few years ago there was a problem with one of the Grom clones, maybe the Vader, having too weak engine mount bolts that broke. But they upgraded theirs too. I would think Grade 8 bolts will be fine. Find out what they use on actual Groms. __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
	1

08-29-2022, 09:59 PM	#4
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,868	OK. So the motor will take 10mm bolts, or the tunnel needs to be slightly enlarged to do so? Or just the mounts need to be opened up? __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
	1

08-30-2022, 09:43 PM	#5
Big Bird Join Date: May 2020 Location: California Posts: 169	Yes many people drill the mounts for the next size up standard or metric bolt. Lately it's been popular to get the aluminum aftermarket bottom mount for a grom and drill holes to match up to the china engines. Typically called the "3rd mount" mod. Grom has 3 mounting points with 10mm bolts from the factory. Even though the clones come with "12.9" stamped bolts they are still garbage that snap. __________________ 2020 Boom Vader Gen 2 2019 CSC TT250 2021 Kayo Fox 70
	3

08-31-2022, 04:26 PM	#8
CheapThrills Join Date: Jan 2021 Location: Lehigh Valley Area Posts: 148	Anyone have the actual steps to replacing and increasing the size of bolts? Like drill out with XXmm drill. Replace bolts with xxmm x xxmm & xxmm x xxmm? Thx, P.S. Haven't increased the engine mount bolts yet, but fixed my recently broken one and remaining stock one with some bolts I bought at the hardware store. Back to riding and now I can take time to properly look into mod'ing the frame for larger bolts. https://mymotorcycleblog.com/boom-va...olts-replaced/ __________________ - My 2 Bikes: TaoTao TBR7 Boom Vader Gen 2 (BD125-10) Testing a YouTube Channel Last edited by CheapThrills; 09-08-2022 at 11:04 AM. Reason: Additional information
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08-29-2022, 07:45 PM	#3
derekracer Join Date: Aug 2022 Posts: 3	I am indeed upgrading them to 10 for the purpose of reducing vibration. There's to much wiggle room on the tunnel portion going through the engine with the stock 8mm bolts. I'm pretty sure the engine is drilled out for 10mm.
	0

08-31-2022, 08:22 PM	#9
derekracer Join Date: Aug 2022 Posts: 3	I currently have 10mm bolts in my possession. I have a 10mm drill bit coming in the mail tomorrow. I hit the frame holes with a 3/8 drill bit (close enough to 10mm hoping the bolt would slide right through. From my research the engine should have a 10mm tunnel running through it and hoping no drilling of engine hole required. I had a very difficult time aligning the 3 holes back together even with a floor jack so I put it on the backburner until this weekend. I will drill out the engine hole if need be though. Ill let you guys know how it goes and what was required.
	1

09-07-2022, 04:06 PM	#10
ripcuda Join Date: Mar 2015 Location: Spokane, WA Posts: 253	I had an engine bolt break on my Hellcat. Resolved this with new 5/16" x 5" (long) Grade 8 bolts from the hardware store. I also welded up an under-engine 3rd mount. No issues since. Pics in the thread linked in my signature. GL. __________________ '20 TaoTao Hellcat 125 "grommet" '04 Yamaha TTR-125LE '00 Yamaha TTR-90 '07 Kinroad XT200GY Runmaster (sold) '07 KMD GY6 150cc ATV (sold) '07 Kangchao 250cc ATV Monster (sold) Baja Moto DB-30 "Doodlebugs"(x3) (sold) '06 Hi-Bird 200 parts bike (sold)
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