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512high

IDLE..WHY SO HIGH?

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Hi everyone, for starters yes I'm a beginner...my 06' Montesa 4RT, owners manual says about 1,800 rpm on idle, can I ask what the reason is for this? When I in first or second gear, I'm trying to learn low speed balance, doing or I should say "trying" to do figure 8, I have to play with the clutch so much to try to slow down etc. I'm sure there is a reason , thought I would ask....

thanks ahead of time

 

philip

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You are going to have to learn how to ride the clutch and brakes to slow it all down.

You may also need to mod the clutch as the early 4RT I had had a very snappy action.

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5 minutes ago, collyolly said:

You are going to have to learn how to ride the clutch and brakes to slow it all down.

You may also need to mod the clutch as the early 4RT I had had a very snappy action.

ya, i am learning(slowly)....but is there an advantage of why so high on the idle? thanks for the reply too

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Following is speculation not definite fact.

High tickover needed to generate sufficient electric to run EFI. Some say engine can stall unexpectedly if tickover turned down. I rode a friends bike with the tickover turned down and it seemed OK

Large bore throttle bodies do not give stable air flow at low RPM. Makes bike performance jumpy / inconsistent during initial throttle opening.

A four stroke cannot produce the same power as a two stroke (of same capacity) without having valve timing to suit high RPM power output. Without VVT this high power / high speed valve timing compromises slow speed running.

At early stages of 4RT development the works riders favoured engine characteristics similar to 2T this means a 4T has to rev twice as fast as a 2T for the same number of power strokes.

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It needs a high idle to keep everything running like clockwork. The idle can be dropped a little (using the adjuster on the left hand side off the throttle body) but not too much as you can encounter starting issues. 

Although the idle seems quite fast, proper throttle and clutch control will allow you to do the figure of 8 as slow and tight as you like. Start off big and give yourself plenty of room. 

Keep at it.

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2 minutes ago, dadof2 said:

Following is speculation not definite fact.

High tickover needed to generate sufficient electric to run EFI. Some say engine can stall unexpectedly if tickover turned down. I rode a friends bike with the tickover turned down and it seemed OK

Large bore throttle bodies do not give stable air flow at low RPM. Makes bike performance jumpy / inconsistent during initial throttle opening.

A four stroke cannot produce the same power as a two stroke (of same capacity) without having valve timing to suit high RPM power output. Without VVT this high power / high speed valve timing compromises slow speed running.

At early stages of 4RT development the works riders favoured engine characteristics similar to 2T this means a 4T has to rev twice as fast as a 2T for the same number of power strokes.

Thank you for the response dadof2! Now i understand, let me ask you or others this...previous owner put an hour meter/tach on it (cheap one as i see), i'm using the hour  side for maintenance, when bike is running, tach all over the place...Is there a way to know for sure that i am around 1,800 rpm? should i buy something else to check? again ty

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Either buy a decent tachometer of pop round to your local garage or engine diagnostics centre. They can attach a sensor to the spark plug lead and tell you the exact RPM using a scope. 1800 RPM = 66.6 m/sec sparking intervals (on a 4T). This should take less than 5 minutes.

 

Edited by dadof2
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9 hours ago, 512high said:

Hi everyone, for starters yes I'm a beginner...my 06' Montesa 4RT, owners manual says about 1,800 rpm on idle, can I ask what the reason is for this? When I in first or second gear, I'm trying to learn low speed balance, doing or I should say "trying" to do figure 8, I have to play with the clutch so much to try to slow down etc. I'm sure there is a reason , thought I would ask....

thanks ahead of time

 

philip

Hi

you need to be working the clutch and brake to be successful in trials so practice this basic skill first as last. The old days of doing turns with the clutch engage are long gone.

i probably have my tick over way above the 1800 to avoid the odd cough and stall and have no issue on the tight stuff even with std gearing.

The early 4rts did benefit from bigger clutch master cyl.

A later model plate clutch plate yes just change one of them I recall to improve and also correct  gearbox oil.

good luck

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When I first got my '05 4RT I felt it was too fast like yours.  I went to a 9 tooth front sprocket (43 rear) and it was a lot better.  I also set my idle at 1900 because it was much less likely to stall when I lugged it too slow.   As my skill improved I was able to do full lot turns at idle with or without using the clutch.  When it was time for a new chain and sprockets I went with a 10:44 set-up (Thanks to Mike at the Tryals Shop in NY for that recommendation) that is perfect for me. 

 

Have fun!

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