GSF250 Problems

[Pin3Appl3]

Hi everyone

So I did a little porting on my 1990 GSF250 head to remove casting flashes and improve the taper of the ports, when I put it back together it ran but was running a little funny, it got harder and harder to start and finally I can't get it to start at all.

Initially

- Ported
- head was reassembled by mate at kalford Cams, I'm sure he would of done it correct
- Valve lap
- original head gasket, re-copper coated

now since the original re-build I have:

- taken it to Duane's Bikes & Skis in Chirstchurch (everyone recommended him), he couldn't get it to go but said he could see anything wrong with fuel system
- replaced head gasket, copper coated, tightened head bolts to 20Nm (if this is wrong would be good to know)
- re-shimed engine to, intake .15-.2mm (6-8 thou), exhaust .2-.25mm ( 8-10 thou)
- replaced air, oil & inline fuel filter filter
- cam timing checked by Kalford Cams mate
- new second hand ignition coils
- new plugs
- no blown fuses
- checked loom for breaks
- cleaned carbs
- checked voltage in to primary side of ignition coil, 40ms duration square wave @ 11v roughly, see below

So I have been thinking that my CDI may have a problem with it, I checked the resistance across the plug terminals and most are in the Meg-Ohms range going off this page

http://www.synapse.ne.jp/s-hara/band....html#electric

the CDI resistance should be in the kil-Ohm range,

I found a post on these CDI's having problems with their capacators, so I replaced them and the resistances dropped by about 15-20% for most of them, but still in te Meg-Ohms range, and no joy from my bike either.

so... any ideas?

[Katman]

If it's insured, speak to Tigertim.

[Pin3Appl3]

If it's insured, speak to Tigertim.

Hi Katman, nah it is not insured

[Paul in NZ]

So you are cranking it and it won't start?

If you pull the plugs are they wet?

Have you got spark at the plugs?

[Pin3Appl3]

So you are cranking it and it won't start?

If you pull the plugs are they wet?

Have you got spark at the plugs?

Hi Paul

ya I am cranking it, after a bit of it cranking the plugs will be wet, there is spark at the plugs but it looks some what weak, when i have one plug in the head and one out the spark is weaker than when i have two out, I'm guessing that it is due to the in cylinder plug being at a higher pressure and it being hard to arc across it, therefore when both are in it mite not be sparking at all.

plug gaps are correct, and I have checked the impedance of the coils to be correct as well

[Brayden]

If it's insured, speak to Tigertim.

Fucking cracked up so hard

[Brian d marge]

Dont get all complicated ,

it was running but got harder and harder

electricity tend to be erratic , ie it will fart around gas tends to be slow and final like its running out of breath

spark at the right time ?

compression anything over 100 psi should do ( ie make it run ) ?

and fuel ( try giving it some , crank it over on ezi start ( be careful) ?

check basics first

When you get it started , now fix problem

Stephen

ps there is more to this than meets the eye one thinks .....

[Pin3Appl3]

Dont get all complicated ,

it was running but got harder and harder

electricity tend to be erratic , ie it will fart around gas tends to be slow and final like its running out of breath

spark at the right time ?

compression anything over 100 psi should do ( ie make it run ) ?

and fuel ( try giving it some , crank it over on ezi start ( be careful) ?

check basics first

When you get it started , now fix problem

Stephen

ps there is more to this than meets the eye one thinks .....

Hi Brian

compression is around 150 psi

I have tried starting it on start ya bastard, down through the carbs

I should be able to get a timing light on to it this weekend to check that the spark is in time

[FJRider]

there is spark at the plugs but it looks some what weak

Plug gaps are correct, and I have checked the impedance of the coils to be correct as well

Try replacing the plugs with new one's ... it reduces the list of possible issues by one.

No matter if the gaps are correct ... if the plugs are dud, it wont go.

[Pin3Appl3]

Try replacing the plugs with new one's ... it reduces the list of possible issues by one.

No matter if the gaps are correct ... if the plugs are dud, it wont go.

Hi FJRider, ya I have already replaced the plugs, I just mentioned tat the gaps were correct so you knew that I had checked them, thanks though

[nzspokes]

Pulse generator.

You can pay me later.

[Pin3Appl3]

Pulse generator.

You can pay me later.

Hi nzspokes, by pulse generator are you meaning the signal generator in the right side of the engine?

[nzspokes]

Hi nzspokes, by pulse generator are you meaning the signal generator in the right side of the engine?

I dont know where it is on your bike but sounds like classic Pulse generator failure.

[Pin3Appl3]

I dont know where it is on your bike but sounds like classic Pulse generator failure.

sweet, I'll look into it

also I checked the timing and it is all good

[Pin3Appl3]

So I got it to start, bit of adjustment with the carbs, possibly the capacitors in the CDI and cleaning of plugs may have lead to it, hard to say which.

However once it had warmed up I started to get that dreadful blue smoke coming out of the head breather hose, and exhaust.

so this means I have either a blown head gasket, warpped head, stuffed rings or hopefully the easiest to fix, I didn't bolt the head down with enough torque, anyone know foe certain what the head bolt torque should be for one of these bikes? currently it is at 20 Nm