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Hey guys, I'm new to the forum and this is my first post so I apologize if this topic has been discussed. I did a couple upgrades to my grom all at once and I'm not sure what couldve went wrong. I put in the high rpm/colder spark plug, tbr full exhaust and did a valve adjustment on the same day. I notice that its really hard to get passed 7.5k ish rpm at wot on 4th gear. My top speed is around 55 ish sitting up and it seems to really struggle to get to 61 with full tuck. Im 5'8 , weigh about 170 and I've seen plenty of posts of bigger guys that can go faster than me so I'm wondering if something is wrong or does my speed sound about right? Could it be the colder spark plug? The full exhaust without a jet kit? I did notice my low end power seems better than before. The ecu has reset since then by the way. I did double check my valve adjustment and it seemed good but I guess I might have to triple check. Any help would be apreciated. Thanks.
 

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You're about the same size as I am, and that was the top speed I reached on flat ground with no head wind while my bike was still stock. After I put on intake/exhaust there was hardly any change except a decrease in low-end torque.

Once I put on a fuel controller, low-end torque was improved by a lot and I was able to reach higher speeds (~62 MPH) and sustain them on flat ground.

Long story short, I would recommend investing in a fuel controller, and probably an intake mod (preferably the Chimera in order to retain IAT sensor and crankcase breather). I bought the Dobeck AFR+ and I'm extremely happy with the results.
 

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Hey guys, I'm new to the forum and this is my first post so I apologize if this topic has been discussed. I did a couple upgrades to my grom all at once and I'm not sure what couldve went wrong. I put in the high rpm/colder spark plug, tbr full exhaust and did a valve adjustment on the same day. I notice that its really hard to get passed 7.5k ish rpm at wot on 4th gear. My top speed is around 55 ish sitting up and it seems to really struggle to get to 61 with full tuck. Im 5'8 , weigh about 170 and I've seen plenty of posts of bigger guys that can go faster than me so I'm wondering if something is wrong or does my speed sound about right? Could it be the colder spark plug? The full exhaust without a jet kit? I did notice my low end power seems better than before. The ecu has reset since then by the way. I did double check my valve adjustment and it seemed good but I guess I might have to triple check. Any help would be apreciated. Thanks.
I've done both of the BBK mods, BrianS 170 BBK kit and the Finbro 183 BBK and you do need to get a A/F monitoring system such as the WB02 sensor and at lease a PCV unit.

Second thing that must be done when you upgrade your exhaust system is to match that system with a good air filter system.

I'm pretty happy with my OEM stock grom air box mod using the BMC air filter unit that HRD sells

The PCV will help you out in trying out various A/F maps that would match your setup.

Big hint, I was texting with a person that builds/designs/makes cams for the Honda Grom/MSX15 and he told me the guys that do race the groms where getting better speed staying with stock engine and installing a better cam and having the grom tuned for the right A/F mixture.

I found that when going BBK that improvements with a port/polished inlet pipe "open up a little" and the plastic spacer bored to match a port/polished head gave me the best HP.

With out having your Grom put on a dyno and having a A/F monitoring system you are shooting in the dark in trying to figure out where to get more HP or increase performance thru out the RPM range.

When I upgraded both of my Groms I put in one mod at a time and went out for a test ride to see if it made any changes to HP or performance and that is what I would recommend that you do. Go back to all stock and install the exhaust system first go out ride and see if you gained or lost HP and if it did not improve than work on the A/F mapping adjustment and airbox mods.

Good Luck.
 

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You're about my size.

I have moriwaki exhaust and modded airbox and my speeds are about the same as yours.

I can't help thinking people talking about 70mph+ are being liberal with the truth, or maybe measuring on a long downhill or have fitted a bigger rear sprocket and get false readings or whatever.

My top speed's been 110kmh on a slight downhill with a light tuck. I don't expect any more than that, it was on the ragged edge and vibrating like mad already.
 

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you need more fuel im sure. when mine was stock except an exhaust i could hit 63-64 and im 15-20 lbs heavier than depending on the day. has the fuel pump recall been done yet?
 

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Discussion Starter #7
I was hoping I didn't have to add a fuel controler, that's why I haven't added the intake or anything else. Do you guys think its running lean to the point ill cause damage if I don't add one? I still haven't had the fuel pump replaced so ill definitely have to look into that. Haha i haven't tried tucking like that yet :p
 

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I did on 12" wheels with a Thai fuel pump and stock gearing 15-34, in perfect conditions 116 km/h tuck (72mph), downhill reached max 126 km/h tuck (78mph). Those are maximum numbers in perfect weather conditions.
Fuel controller is not that expensive.
IMG_20140924_165557.jpg
 

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DCR Cam, MNNTHBX exhaust, Bazzaz fuel programmer with Chimera intake and 70 isn't a problem. Not sure why you changed your spark plug to a colder plug, was your other plug ash white or glossy? I bet your new plug is going to foul black in a hurry. The colder plug doesn't produce more or less energy than a hot plug, it has greater resistance to heat so it will just foul faster than a "hot" plug or not burn up as fast as a hot plug. It's just a thicker insulator around the tip of the plug and that's usually the only difference.

Right now, you're right on track for the money you've spent. Keep throwing money at it and it will go faster and handle better, I promise.
 

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I put the cold plug cause I read somewhere that its good to use a cold plug if your running high rpms most of the time which is how I ride. I havent checked it but now you got me thinking. Ill probably just switch back to the stock one. Damn this hobby gets expensive!
 

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I wouldn't worry about the plug, keep the colder one in. I didn't see above 55 untucked until I got about 450 miles in even with full exhaust and fuel controller. Now that I'm broken in I can see 57-58 untucked, and 64 full tuck on level ground. Is your Grom still new?
 

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i'd try to put your stock exhaust back on and see if you see any positive changes. the odd part is a free flowing exhaust tends to hurt the low end and improve the high end. with your setup, you seem to have the opposite. i'd also triple check your clearances. what are you using?
 

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i'd try to put your stock exhaust back on and see if you see any positive changes. the odd part is a free flowing exhaust tends to hurt the low end and improve the high end. with your setup, you seem to have the opposite. i'd also triple check your clearances. what are you using?
I think that's (together with noise limits) why Moriwaki have done some magic with chambers.

 

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Yeah I'd be happy if I can reach 58 comfortably while sitting up. I have over 2600 miles on it now. I might switch back to the stock exhaust. The valves are set at what the service manual recommends and I made sure they where right on the gauge but maybe after riding the nut got tighter/looser?
 

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when doing valve adjustments, it's good to double check after 100 or so miles. also, make sure you're really at tdc. to help ensure i'm at tdc, in addition to removing the inspection cover on the crankcase, i remove the side cover on the cylinder to use the markings on the cam gear.
 

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Oh ok, I didn't check it after I put it all back together. Ill check it this weekend. So what side cover on the cylinder do you mean? Are you talking about the one where the t and the f show when you turn the engine?
 

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Yeah I'd be happy if I can reach 58 comfortably while sitting up. I have over 2600 miles on it now. I might switch back to the stock exhaust. The valves are set at what the service manual recommends and I made sure they where right on the gauge but maybe after riding the nut got tighter/looser?
i've recently discovered that if i sit at WOT for a prolonged time, the bike slows down and struggles to go faster than 50. if you ease off slightly to a point that the bike doesn't lose speed, it should start to pick up. I done nearly 200 miles on it this weekend and a lot of those were motorway miles and was happy once I discovered that!
 

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Hey guys, I'm new to the forum and this is my first post so I apologize if this topic has been discussed. I did a couple upgrades to my grom all at once and I'm not sure what couldve went wrong. I put in the high rpm/colder spark plug, tbr full exhaust and did a valve adjustment on the same day. I notice that its really hard to get passed 7.5k ish rpm at wot on 4th gear. My top speed is around 55 ish sitting up and it seems to really struggle to get to 61 with full tuck. Im 5'8 , weigh about 170 and I've seen plenty of posts of bigger guys that can go faster than me so I'm wondering if something is wrong or does my speed sound about right? Could it be the colder spark plug? The full exhaust without a jet kit? I did notice my low end power seems better than before. The ecu has reset since then by the way. I did double check my valve adjustment and it seemed good but I guess I might have to triple check. Any help would be apreciated. Thanks.
sounds about right ?

guys claiming 70+ on the daily with only an exhaust are over compensating for something

intake,exhaust,tune is still only going to get you 65+
 
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