Honda Grom banner
1 - 20 of 20 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter · #1 ·
replacement of Fuel injector yuminashi Light bore
I have tried on a standard engine, Ful X- seed Exhaust - 2 x 20 mm Holes i the airbox
it has not influenced very much on performance - a little on top speed 105 -- 107 at the best, compared stock 100 -- 102
engine seems quite indifferent, with exhaust air filter ASO

actually I thought the engine pulls best standard,only with slipon exhaust Damper
I've tried 14 t 15t 16 t gear, the best is 15 standard in combination with injector exhaust air filter
My final conclusion is do you want more power in your Grom -must be installed BigBore
I think honda has made ​​a super fine little machine, but lacks off power
just my opinion after several attempts to get a little more Power in the engine
 

Attachments

·
Registered
Joined
·
225 Posts
my light bore injector has just arrived. Will fit it tomorrow night and have a play. I've got an open stack and nearly open pipe, so there should be enough air to make it worth while. Fingers crossed!
 

·
Registered
Joined
·
357 Posts
If I cant get decent power from mine for a large outlay of cash al end up selling it next year, I miss my tmax scooter!
 

·
Registered
Joined
·
1,283 Posts
Im fairly sure just replacing the injector won't do a lot unless you have the ability to map the ECU, that would require an FI module and dyno time. an injector is told by the ECU when to open and for how long, the injector is measured in flow of fuel by pounds per hour. Fuel pressure also is a factor. Replacing the stock injector is like putting a different jet in a carb but the results will be nothing like changing a jet. If the injector is rated at a higher flow per hour you will get more fuel but only for the same duration and pulse length of the stock injector determined by the ECU.

A stock motor with a higher flow rate injector is likely to run worse. We need programmable ECU or piggy back units to become avaiable. I'm waiting on those.
 

·
Registered
Joined
·
225 Posts
how did you reset your ecu? mine started running fine the first night after the first mile, but the next day reverted back to just bogging down the whole time. Any ideas?
 

·
Registered
Joined
·
225 Posts
tried that, once for 2-3 mins, once for 4 hours! No joy.
 

·
Registered
Joined
·
955 Posts
I put the performance injector in two weeks ago and it ran way too rich. It didn't want to go above 6k RPM then it would bog because of too much fuel. I think on a stock bore it is overkill and the stock injector is optimized already or the best AF mixture. Most likely you will see the best results after a bigger bore and new exhausted is installed. I don't recommend or think this injector is necessary on the stock bore with a stock cam and exhaust.
 

·
Registered
Joined
·
6 Posts
Disconnecting the battery does not reset the ecu it actually says that in the manual.
To reset you have to remove the cap from the DLC and "jump" the green/black to the blue/black wire whilst the ignition is off twist the throttle fully open and hold it open whilst you turn ignition on. The engine light will come on then start flashing rapidly.
When rapid flash starts you have 5 seconds to snap it closed then after 3 seconds it will flash the successful pattern(1 short blink followed by a long space repeatedly. Yes should be done whenever you change anything that will effect the Ecm's algorithms but doesn't necessarily have to be as the Honda's ecm constantly rewrites itself using the data from the sensors. This is why it comes good after a mile or 10. That being said a test run where it runs like shit is a fail in my books.
I did exhaust + reset, test ok
Intake + reset,ok
Yep valves, piston(replaced stock w stock 40,000km on the clock reset, ok
Started to run rough and not really idle so well, so I'm thinking clean the throttle, replace the injector or valve not closing so I went with the easiest option and bought the 15dollar 170cc injector.
After installation and a reset I had to turn the idle air screw out another whole turn to even get it to start. I knew something wasnt right but I took it around the block anyway and sure enough it ran like shit. Probably 1 more lap and it might have been fine but tbh 1 lap was embarrassing enough. I wheeled her in reset it again turned the idle screw to factory and same thing ,needed another turn out to start and idle so I took a step back, scratched the melon for a sec and thought I'd give altitude mode2 a shot (same procedure as reset but snap closed for .5 of a second, opened again for .5 snap closed and wait 3 seconds for successful pattern. Idle screw to stock
2 turns out .
Bam started , idled like it should.
test lap=spot on
 

·
Registered
Joined
·
6 Posts
Disconnecting the battery does not reset the ecu it actually says that in the manual.
To reset you have to remove the cap from the DLC and "jump" the green/black to the blue/black wire whilst the ignition is off twist the throttle fully open and hold it open whilst you turn ignition on. The engine light will come on then start flashing rapidly.
When rapid flash starts you have 5 seconds to snap it closed then after 3 seconds it will flash the successful pattern(1 short blink followed by a long space repeatedly. Yes should be done whenever you change anything that will effect the Ecm's algorithms but doesn't necessarily have to be as the Honda's ecm constantly rewrites itself using the data from the sensors. This is why it comes good after a mile or 10. That being said a test run where it runs like shit is a fail in my books.
I did exhaust + reset, test ok
Intake + reset,ok
Yep valves, piston(replaced stock w stock 40,000km on the clock reset, ok
Started to run rough and not really idle so well, so I'm thinking clean the throttle, replace the injector or valve not closing so I went with the easiest option and bought the 15dollar 170cc injector.
After installation and a reset I had to turn the idle air screw out another whole turn to even get it to start. I knew something wasnt right but I took it around the block anyway and sure enough it ran like shit. Probably 1 more lap and it might have been fine but tbh 1 lap was embarrassing enough. I wheeled her in reset it again turned the idle screw to factory and same thing ,needed another turn out to start and idle so I took a step back, scratched the melon for a sec and thought I'd give altitude mode2 a shot (same procedure as reset but snap closed for .5 of a second, opened again for .5 snap closed and wait 3 seconds for successful pattern. Idle screw to stock
2 turns out .
Bam started , idled like it should.
test lap=spot on
Started running rough *after a month or so
 

·
Super Moderator
2020 Honda Grom
Joined
·
1,490 Posts
What year is your bike? The SF should keep the stock injector unless you go big bore, or maybe ported head. The OG I think needs one much sooner.
 

·
Registered
Joined
·
6 Posts
What year is your bike? The SF should keep the stock injector unless you go big bore, or maybe ported head. The OG I think needs one much sooner.
The local shop only had bigger ones in stock. That's that every ody runs here and it's going fine on altitude mode 2
they do the same thing after big bore installs too.
Big bore and injector no need for programmable ecu. The stock one learns what it needs from the sensors, a reflash is good for unlocking rpm limiter and advancing timing for high comp rigs
 

·
Registered
2020 Honda Monkey and others
Joined
·
968 Posts
The local shop only had bigger ones in stock. That's that every ody runs here and it's going fine on altitude mode 2
they do the same thing after big bore installs too.
Big bore and injector no need for programmable ecu. The stock one learns what it needs from the sensors, a reflash is good for unlocking rpm limiter and advancing timing for high comp rigs
DynoJet said you need bigger injector when you increase the flow through your head with porting, big valves, and larger throttle body.

When I brought my bike to be dyno tuned with stock head and stock throttle body and 181 kit they said the injector was too large.

They still tuned it and made it run well with the bigger injector.
 

·
Registered
Joined
·
6 Posts
Mine is not ported but I did just do valve and piston replacement and I set the valve lash to the smaller end of the tolerances so they were nice and snug and therefore the valves would be opening more and I have increased flow by means of intake and exhaust but it did run fine for about 5 weeks after new valves and piston so I went for the injector first basically because its the easiest and cost the same as a can of cleaner next was cleaning the throttle then prob check the head assembly I have found a piece of gasket goo stopping a valve from fully closing g
 
1 - 20 of 20 Posts
Top