YZF600r Thundercat

[dazzydecks]

Hi,

This is my first post on these forums.

I have a 1998 Thundercat, with approx 23,000 miles on it.

Recently, I took an approx 100mile ride, and stopped the bike, and came back to ride home after about an hour.

The bike had been parked on quite an incline, and when i tried to start, the starter turned the engine as normal, but it would not fire. I tried this for maybe 30-40 seconds (the starter was still spinning quickly) then decided to bump start, which worked ok (if a little reluctantly).

On the way home, after a stop (for a coffee) the bike now wouldn't turn over - it was like a pretty flat battery. Again, bump starting worked, no problem this time.

During the last stage of the ride home, at about 60-70mph on a dual carriageway, the bike started spluttering, and backfiring, and as I came to a roundabout, and had to stop, as the clutch went in, the engine died.

Again, the battery didn't have the power to turn the starter, so I had the dubious pleasure of bump starting it on a dual carriage way, at the entrance to a roundabout, which is quite a fast road

Next time I tried the bike (next night) I used jump leads to start it, and gave it a run out. It now didn't seem to have much power. Possibly like it was running on 3 cylinders.

I got home, and put the battery on charge, and then had it tested to see if was holding charge; it was.

Further rides have been similar. When accelerating hard in 2nd, it used to be like a rocket ship taking off; it's now like a boy racer's hot hatch. It still carries on to high speed, but there is something wrong at the lower end.

I haven't had problems with starting the bike since.

Are the problems all related? Have I caused problems by bump starting it? Is it something as simple as the sparkplugs need readjusting/replacing, or is the fuel pump to blame. Alternator?

I have very limited knowledge, and would appreciate the help.

Thanks in advance. If there is any infomation required that I haven't provided, just give me a shout!

Cheers,

Darren

[chrisw]

Get the Alternator checked to make sure it's pushing out enough power to run the bike and charge the battery. Or maybe the battery is on it's way out, possibly even the rectifier/regulator is intermittently playing up.

The odd bump start shouldn't cause a problem, so I wouldn't imagine the starting problems are related to you running concerns, but if it's not running right cover the basics first, such as:

i) Are the Spark plugs in good condition. Remove, Clean and replace if necessary.

ii) Is the air filter clogged up. Remove inspect and replace if necessary

iii) Are the plug leads in good condition. remove a plug and hold it in with some insulated pliers

touch the electrode against the engine and turn the starter motor, you should see the spark

between the electrodes, also run the bike (all assembled) in the dark (unlit garage) to see if

the current is escaping through the leads and arcing across each other)

iv) Are the carbs syncronised correctly.

After ruling these out then if the problem is still apparent and not in the head (according to some mechanics 90% of running problems are actually in the riders head and nothing is wrong with the bike). then you need to think about getting a competent mechanic to have a look at it.

[Mark yzf600]

ive had the same trouble with my first car.

if your battery is old it will charge fully but will not hold a charge completely and start to affect the engine the more power you consume ie brake lights , head lights.

buy a new battery ,,if problems persist get a diagnstic done on alternator.

[dazzydecks]

Hi,

Thank you for your assistance.

I took the bike to a (competent??) mechanic, who sync-ed the carbs, and whilst this solved the backfiring issue, it still doesn't run right (see below).

The mechanic told me that this could be due to the self-adjusting cam belt, and it may sort itself in due course (really?).

He also mentioned that the exhaust pipes are corroding, and will need replacing but he didn't want to do that in November as the cold weather would mean that the expansion/shrinking of pipes would mean the quality of the work wouldn't be quite good enough (again, is this actually true??).

Now, you might wonder why I didn't question this work, but the garage had had my bike for almost 5 weeks before I got it back, and the constant barrage of lies I faced about when it would be ready meant that I just wanted to take it away from them.

As it is pretty wintry, I haven't ridden it so much, but on the occasion that I have, it pulls better than it did before the original episode, but it sounds like a bag of spanners (and idle is all over the place), and I'm pretty sure the racket is coming from the head of the engine where the exhaust pipes attach.

The battery issue is still there, but less so (somehow) and I will be replacing the battery ni the next week or so. Hopefully that should deal with the starting/charging issue.

If we assume that the exhaust isn't sound, what impact would the repair/replacement have on performance?

Any other tips would be useful - I'm planning to ride from uk to Spain in the summer, but as it stands I wouldn't trust it.

Thanks very much guys,

Darren

[dazzydecks]

In response to chrisw's reply, I have checked and replaced the spark plugs (they seemed ok, but I thought better safe than sorry).

I haven't yet checked the air filter. I will check it this weekend.

It doesn't have the same 'running on 3 cylinders' feel as before - I presume the syncing of the carbs solved this problem. The change in spark plugs offered no noticable improvement to performance or tickover.

Regards,

Darren

[chrisw]

Hi Darren

Sounds like your mechanic is talking out his rear end, I've never heard anyone say they can't replace an exhaust in winter cos the pipe contracts. dfoes he not have a warm workshop.

I think the most likely reason is that the studs that hold the header pipe become quite corroded and often snap when undoing the bolts to remove the old header pipe. This happened on my old 2001 TCat at approx the same milage. I was lucky in that I could just get the nut on enough afterwards to secure the new header pipes. (replace with Stainless stell pipes so you don't have to replace them again.) If they do snap and there's not enought thread left, it's a drilling out job which is quite difficult. to get spot on straight.

Saying that it sounds like a bag of spanners could be because of the gasses escaping from the holes in the exhaust. This could be why the idle is unrestful.

Did the mechanic check the Cam belt Automatic Adjuster, it may be past it's best and not have enough tension to keep the chain taut alowing for cam chain rattle, also making idles unrestful. I'd phone a main dealer and see how much they are to replace.

As far as the battery goes, did you get the Alternator checked, if this caused the battery to flatten then a discharged battery is likely to become faulty and not be able to be restored meaning a new battery is needed. Only replace though if your sure the Alternator is OK as you don't want to kill your new battery.

[600tcat]

Exactly the same happened to my 98 cat when i didnt hook up the trickle charger after a run out. The alarm/immobiliser drained the battery. Bumped ok but cut wouldnt idle & backfired seemed to lack power etc.

New battery fitted, all sorted, no more probs.

Good luck