Hard starting 750 brute
#1
02-02-2009, 07:58 AM
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Hard starting 750 brute
I am working on a 2005 BF, its hard to start, the front carb has a smaller main jet than the rear, 147.5 verses 152.5, I seem to remember a recall or service bulliten about this but cant get the search to work, does anyone remember the cure for this? I think the jets should at least be the same in both carbs, what do you think?
#3
02-03-2009, 11:17 AM
Hard starting 750 brute
<div class="FTQUOTE"><begin quote>Originally posted by: Kerbbirds
Does anyone care?</end quote></div>
Got to wait a little...
My 750 manual (P/N 99924-1334) on page 3-6 says that:
Front Main Jet is 152
Rear Main Jet is 158
Also, the jet needles are different. Front one is leaner.
However, above difference has NOTHING to do with the hard starting issue, because main jets and jet needles affect mid to top rpm range only. The reason for front carb is set leaner is because the front cyl has hotter operating temp than the rear one. Hotter means less dense air requiring less fuel. And the reason for the front one to run hotter is because all the heat from the front head pipe is soaking onto the front cyl. In contrast, the rear head pipe is postioned behind the rear cyl and it doesn't affect as much.
The service bulleting you were talking about is regarding the jet needle change (to fatter one) on the front carb to cure the intake popping/hesitation - again, NOTHING to do with the hard starting.
The hard starting on the 2005 BF750 is not a common problem (and I have the same model). Mine starts every time even after sitting not used for weeks. Something must have gone wrong on yours and I would check:
> Plug fouled?
> Pilot jet clogged?
> Staled fuel?
> Tight valves?
> Compressiong low?
> Choke plunger stuck?
There are handful of things to check.
Does anyone care?</end quote></div>
Got to wait a little...
My 750 manual (P/N 99924-1334) on page 3-6 says that:
Front Main Jet is 152
Rear Main Jet is 158
Also, the jet needles are different. Front one is leaner.
However, above difference has NOTHING to do with the hard starting issue, because main jets and jet needles affect mid to top rpm range only. The reason for front carb is set leaner is because the front cyl has hotter operating temp than the rear one. Hotter means less dense air requiring less fuel. And the reason for the front one to run hotter is because all the heat from the front head pipe is soaking onto the front cyl. In contrast, the rear head pipe is postioned behind the rear cyl and it doesn't affect as much.
The service bulleting you were talking about is regarding the jet needle change (to fatter one) on the front carb to cure the intake popping/hesitation - again, NOTHING to do with the hard starting.
The hard starting on the 2005 BF750 is not a common problem (and I have the same model). Mine starts every time even after sitting not used for weeks. Something must have gone wrong on yours and I would check:
> Plug fouled?
> Pilot jet clogged?
> Staled fuel?
> Tight valves?
> Compressiong low?
> Choke plunger stuck?
There are handful of things to check.
#4
02-17-2009, 07:18 PM
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