Quick RPM question...

[Hughieboy]

Evening All,

I recently rebuilt my Li motor.
GT186 kit
30mm PHBH Dellorto jetted as recommended by Richard Taylor
TSR Evo pipe
Varitronic ignition set to 19 degrees btdc
Runs nice and cool at around 80 degrees c according to the cht gauge on a SIP speedo (sensor fitted to spark plug nut)

Starts, runs and rides great. But doesn’t seem to want to rev past about 7000rpm.

Pulling over 60mph at that so not a huge issue but would go more if it would rev more.

Any ideas?

[rossclark]

Might be worth trying a pipe that lets it rev on more.

If the TSR pipe is similar to the JL3 / Taffspeed they can run out of puff about there.

What's your gearing?

[Hughieboy]

Gearing is Pacemaker gears 17/46....

Was 16/46 but was ‘all powerband’ so to speak...

It’s not struggling to pull the gearing, it’s just not revving that high. I was under the impression that the TSR was quite a high revving expansion...

I haven’t tried a JL3 or Taffspeed so can’t compare...

[dickie]

Varitronic should be at about 24 btdc at about 2000rpm as it retards 8 degrees.

If you're at 19 when it's at low rpm, I'm surprised it's even getting to 7000.

[Hughieboy]

Varitronic should be at about 24 btdc at about 2000rpm as it retards 8 degrees.

If you're at 19 when it's at low rpm, I'm surprised it's even getting to 7000.

Where does that come from? This is where I get confused...

Cam Lam recommend 21 btdc if using a Clubman, 19 if using an expansion. It’s in the fitting instructions....

[Hughieboy]

My main concern would be not advancing to the point of getting heat problems.

My old kit used to heat seize all the time, I don’t want to do that with the new GT186 kit..... but equally I’m not sure what a safe operating temperature is. Currently it runs at about 80 degrees, so I guess there’s room to go hotter than that...

[MickYork]

I set my Varitronic (on an Avanti) at 25*. at 6000 rev's it came down to 17/18 degree and probably a bit lower when the rev's went higher. This was with a Franspeed Race. I didn't monitor the heat but had no problems.

[Hughieboy]

I set my Varitronic (on an Avanti) at 25*. at 6000 rev's it came down to 17/18 degree and probably a bit lower when the rev's went higher. This was with a Franspeed Race. I didn't monitor the heat but had no problems.

I guess I tend to read things and take them as gospel as I don’t understand enough to know better.... I’ll maybe try advancing the timing a tad... thanks.

[missing lynx]

A side issue I wouldn't use the heat sensor ring under the plug I know a couple of lads that have had their plugs come loose as the soft metal on the ring compresses when hot

[Hughieboy]

A side issue I wouldn't use the heat sensor ring under the plug I know a couple of lads that have had their plugs come loose as the soft metal on the ring compresses when hot

What I do is slide it over the plug body and rest it on the nut then hold it in place with a thin piece of rubber hose then fit the cap over that to hold it all in place.... probably not 100% accurate but pretty close I should think..