Engine dies at the end of the straight?

**grantman** · 24th April 2009, 19:36

When I was at MT wellington I changed the front sprocket to a 11 tooth for my GRC rep & It has made the power a lot less peaky and now alot smoother out of corners
Gives better top speed down the stright too

Thanks Gadgit for your help

But I noticed a couple of times the engine died as I come down the stright and closed the throttle for the corner.

When I went to the side of the track I was unable to restart it
UNTIL I put the choke on
Then first pull and it fires into life
Turn the coke off and do 2 more laps

Then same thing ...dies after closing the throttle for the sharp corner.

I find it very strange to have to use full choke to get it to start

I was talking it easy into the corner and would have shut off the throttle a bit too early.
(still getting used to the new gearing...well thats my excuse)

You guys got any idea's?

Thought maybe getting air somewhere ?
Choke may not be sealing correctly?

Any thoughts?

Otherwise all was going well
Its now A LOT QUICKER than my daytona!

**BigAl** · 24th April 2009, 20:49

Hey Grant,

My grc rep requires choke to start even when warm as well, no drama as starts w/o flooding.

As for dying occasionally, check the fuel hose at carb end, hose can be loose on carb and slide/leak. Could also be a filter problem and they like to run with a decent amount of fuel as when leaned over can suck in air from the tank.

Also how'd your brother and mate go on the buckets?

**Gadgit** · 24th April 2009, 21:08

A few things to check like Al said check your fuel hose and maybe float leavel... but the major thing to do is remove the fuel cap strip and drill the air bleed hole large (slightly) then add a small washer between the top part of the cap and the center section of the cap so as the air can get in there... it sounds like it's just running out of fuel at the end of the straight.

**CookMySock** · 24th April 2009, 21:14

Try temporarily removing the fuel filter and see if that improves it. Another test for the same condition, is to lift the back wheel and hold the throttle full open, and see if after 15 seconds or so ir revvs up slightly then quits suddenly. If so, its funning out of fuel.

Steve

**Gadgit** · 25th April 2009, 08:17

Not to sure if I would let a reverse engine free rev for to long... they run very lean at the top end and will happly over rev with no load... But the idea is there DB

**dirtybomb** · 25th April 2009, 11:02

Hey mate,

I had the same problem on my GRC rep, bloody annoying! It ended up being the float level not being set right. Its hard to explain, but pull the bottom of the carb and you will find a small metal tab that you can bend back or foward slightly, which regulates how much fuel enters the bottom part of the carb.

The other thing, if your carb is not mounted straight up and down (i.e on an angle) the float system will not let enough fuel through (due to gravity) especialy after a back straight run.

You have to use the choke to re-start because it needs to pull the fuel through the carb again as it has starved. Mine did this also.

Now mine will start without the choke, even when hot.

Hard to explain the float system, but pull the bottom off the carb and you should be able to figure it out.

Hope this helps.

**CookMySock** · 25th April 2009, 15:02

Originally Posted by Gadgit

Not to sure if I would let a reverse engine free rev for to long... they run very lean at the top end and will happly over rev with no load... But the idea is there DB

Ok, what is a reverse engine?

Steve

**Z1_ZPF_BOY** · 25th April 2009, 15:18

Originally Posted by DangerousBastard

Ok, what is a reverse engine?

Steve

A reverse engine is an engine where the chain and clutch comes out on the right side of the bike such as grc rep, Polini GP3 reverse, gp3 rep. unlike normal bikes which have them on the left side.

**DELLORTO** · 25th April 2009, 16:00

Originally Posted by Z1_ZPF_BOY

A reverse engine is an engine where the chain and clutch comes out on the right side of the bike such as grc rep, Polini GP3 reverse, gp3 rep. unlike normal bikes which have them on the left side.

no your wrong......it means the piston is up-side-down and the crank turns in reverse , also it means the exhaust sucks in gases instead of blowing them out.

thats your problem grant, bloody polini......

**dirtybomb** · 25th April 2009, 22:22

Could you be more specific Max?

I thought the engine just rotated clockwise, rather than anti-clockwise thus having a driveshaft transmitting power to the opposite side (front sproket).

'exhaust sucks in gases instead of blowing them out' What do you mean?

Does anyone know why Polini would design such an engine to rotate the oposite way? Is it because of balancing, centre of gravity maybe?

**DELLORTO** · 25th April 2009, 22:31

Originally Posted by dirtybomb

Could you be more specific Max?

I thought the engine just rotated clockwise, rather than anti-clockwise thus having a driveshaft transmitting power to the opposite side (front sproket).

'exhaust sucks in gases instead of blowing them out' What do you mean?

Does anyone know why Polini would design such an engine to rotate the oposite way? Is it because of balancing, centre of gravity maybe?

its because the crank is situated up-side-down and the motor works the opposite, the exhaust is just there for looks and effect.......the gases actualy evaporate in side the motor,

thats why the exhaust sucks the gases in....so that the motor rev higher

**Gadgit** · 25th April 2009, 22:38

Originally Posted by DELLORTO

no your wrong......it means the piston is up-side-down and the crank turns in reverse , also it means the exhaust sucks in gases instead of blowing them out.

thats your problem grant, bloody polini......

LOL WTF
Haha
THe reverse engine: crank runs opposite to normal minimoto engines Clutch out one side and drives out the other via a 2:1 gear box.

Advantage Toque and it also runs a twin spark ignition More toque...

You must have seen Loosie from team penisular pirates his top bike (GP3) runs a reverse engine

**xtreme** · 25th April 2009, 22:48

Got to agree with you on this one Gadgit !!

What a laugh on that explanation of a reverse engine , upside down piston , backward crank or whatever !!!!! LOL LOL Exhaust sucks Ha Some one blows !! So what does the carb do then ?

**Gadgit** · 25th April 2009, 23:59

Originally Posted by xtreme

Got to agree with you on this one Gadgit !!

What a laugh on that explanation of a reverse engine , upside down piston , backward crank or whatever !!!!! LOL LOL Exhaust sucks Ha Some one blows !! So what does the carb do then ?

LOL
Yea max not to sure where your getting your info for the reverse engine for but it's all wrong...

It only gets it's name from the fact it runs in reverse to the norm to other minimoto engines.... Other wise it's just a 2 smoke engine with a difference of twin spark and a 2:1 gear box